184 lines
7.1 KiB
Plaintext
184 lines
7.1 KiB
Plaintext
{
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"cells": [
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{
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"cell_type": "code",
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"execution_count": 2,
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"metadata": {},
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"outputs": [],
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"source": [
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"from dataclasses import dataclass\n",
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"\n",
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"@dataclass\n",
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"class PropertyFinanceParams:\n",
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" \"\"\"Tunable parameters that describe the finances of a property.\"\"\"\n",
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" purchase_price: float\n",
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" deposit_amount: float\n",
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" loan_duration_years: int\n",
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" lmi_amount: float\n",
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" annual_rental_income: float\n",
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" annual_rental_growth_rate: float\n",
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" annual_interest_rate: float\n",
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" annual_growth_rate: float"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 3,
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"metadata": {},
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"outputs": [],
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"source": [
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"def calculate_stamp_duty(purchase_price: float, first_home: bool) -> float:\n",
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" if first_home:\n",
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" if purchase_price < 600000:\n",
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" return 0\n",
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" elif purchase_price < 605000:\n",
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" return 1045\n",
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" elif purchase_price < 625000:\n",
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" return 5428\n",
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" elif purchase_price < 650000:\n",
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" return 11356\n",
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" elif purchase_price < 675000:\n",
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" return 17785\n",
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" elif purchase_price < 700000:\n",
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" return 24713\n",
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" elif purchase_price < 725000:\n",
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" return 32141\n",
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" elif purchase_price < 745000:\n",
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" return 38444\n",
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" else:\n",
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" return\n",
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" else:\n",
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" if purchase_price < 25000:\n",
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" return purchase_price * 0.014\n",
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" elif purchase_price < 130000:\n",
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" return 350 + (purchase_price - 25000) * 0.024\n",
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" elif purchase_price < 960000:\n",
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" return 2870 + (purchase_price - 130000) * 0.06\n",
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" elif purchase_price < 2000000:\n",
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" return purchase_price * 0.055\n",
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" else:\n",
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" return 110000 + (purchase_price - 2000000) * 0.065\n",
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" \n",
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"def calculate_annual_repayments(principal: float, annual_interest_rate: float, loan_duration_years: int):\n",
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" return (principal * annual_interest_rate * (1 + annual_interest_rate) ** loan_duration_years) / ((1 + annual_interest_rate) ** loan_duration_years - 1)"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 4,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Upfront Costs: 321500.00 = 250000.00 deposit + 0.00 LMI + 71500.00 stamp duty\n",
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"Annual Mortgage Payment: 81241.59\n",
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"\n",
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"Total Paid: 2437247.81\n",
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"Property Value: 9895931.56\n",
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"Total Interest Paid: 1387247.81\n",
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"Total Rental Income: 116762.31\n",
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"\n",
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"Total Paid (10yr): 812415.94\n",
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"Property Value (10yr): 2557296.76\n",
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"Total Interest Paid (10yr): 650510.03\n",
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"Total Principal Paid (10yr): 161905.91\n",
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"Total Rental Income (10yr): 432219.86\n",
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"Net Cash Position (10yr): -380196.08\n",
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"Loan Balance (10yr): 888094.09\n",
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"Total Equity (10yr): 1669202.67\n"
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]
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}
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],
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"source": [
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"def run_simulation(property_finance_params: PropertyFinanceParams):\n",
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" initial_loan_amount = property_finance_params.purchase_price - property_finance_params.deposit_amount\n",
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" yearly_loan_balance = [initial_loan_amount]\n",
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"\n",
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" stamp_duty = calculate_stamp_duty(property_finance_params.purchase_price, first_home=False)\n",
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" upfront_costs = stamp_duty + property_finance_params.deposit_amount + property_finance_params.lmi_amount\n",
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"\n",
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" print(f\"Upfront Costs: {upfront_costs:.2f} = {property_finance_params.deposit_amount:.2f} deposit + {property_finance_params.lmi_amount:.2f} LMI + {stamp_duty:.2f} stamp duty\")\n",
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"\n",
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" annual_mortgage_payment = calculate_annual_repayments(initial_loan_amount, property_finance_params.annual_interest_rate, \n",
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" property_finance_params.loan_duration_years)\n",
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" \n",
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" print(f\"Annual Mortgage Payment: {annual_mortgage_payment:.2f}\")\n",
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"\n",
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" yearly_interest_paid = []\n",
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" yearly_principal_paid = []\n",
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" yearly_property_value = [property_finance_params.purchase_price]\n",
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" yearly_rental_income = [property_finance_params.annual_rental_income]\n",
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"\n",
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" for year in range(property_finance_params.loan_duration_years):\n",
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" interest_paid = yearly_loan_balance[-1] * property_finance_params.annual_interest_rate\n",
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" yearly_interest_paid.append(interest_paid)\n",
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" yearly_principal_paid.append(annual_mortgage_payment - interest_paid)\n",
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"\n",
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" yearly_loan_balance.append(yearly_loan_balance[-1] - yearly_principal_paid[-1])\n",
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"\n",
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" yearly_property_value.append(yearly_property_value[-1] * (1 + property_finance_params.annual_growth_rate))\n",
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"\n",
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" yearly_rental_income.append(yearly_rental_income[-1] * (1 + property_finance_params.annual_rental_growth_rate))\n",
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"\n",
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" if yearly_loan_balance[-1] <= 0:\n",
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" break # Loan fully paid off\n",
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"\n",
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" print()\n",
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"\n",
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" print(f\"Total Paid: {annual_mortgage_payment * property_finance_params.loan_duration_years:.2f}\")\n",
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" print(f\"Property Value: {yearly_property_value[-1]:.2f}\")\n",
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" print(f\"Total Interest Paid: {sum(yearly_interest_paid):.2f}\")\n",
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" print(f\"Total Rental Income: {yearly_rental_income[-1]:.2f}\")\n",
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"\n",
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" print()\n",
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"\n",
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" print(f\"Total Paid (10yr): {annual_mortgage_payment * 10:.2f}\")\n",
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" print(f\"Property Value (10yr): {yearly_property_value[10]:.2f}\")\n",
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" print(f\"Total Interest Paid (10yr): {sum(yearly_interest_paid[:10]):.2f}\")\n",
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" print(f\"Total Principal Paid (10yr): {sum(yearly_principal_paid[:10]):.2f}\")\n",
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" print(f\"Total Rental Income (10yr): {sum(yearly_rental_income[:10]):.2f}\")\n",
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" print(f\"Net Cash Position (10yr): {sum(yearly_rental_income[:10]) - (annual_mortgage_payment * 10):.2f}\")\n",
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" print(f\"Loan Balance (10yr): {yearly_loan_balance[10]:.2f}\")\n",
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" print(f\"Total Equity (10yr): {yearly_property_value[10] - yearly_loan_balance[10]:.2f}\")\n",
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"\n",
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"\n",
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"run_simulation(\n",
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" PropertyFinanceParams(\n",
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" 1300000,\n",
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" 250000,\n",
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" 30,\n",
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" 0,\n",
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" 36000,\n",
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" 0.04,\n",
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" 0.066,\n",
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" 0.07)\n",
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")"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "investment-simulator-KPfGkdIO-py3.12",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.12.0"
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},
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"orig_nbformat": 4
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},
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"nbformat": 4,
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"nbformat_minor": 2
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}
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