Rent vs. Buy Calculator

def rent_vs_buy(
    home_price, down_payment, annual_rate, years,
    monthly_rent, rent_increase_rate=0.03,
    home_appreciation=0.04, investment_return=0.07,
    property_tax_rate=0.012, maintenance_rate=0.01
):
    loan = home_price - down_payment
    monthly_rate = annual_rate / 100 / 12
    n = years * 12
    monthly_pi = loan * (monthly_rate * (1 + monthly_rate) ** n) / ((1 + monthly_rate) ** n - 1)

    # Buying costs over years
    total_mortgage = monthly_pi * n
    total_tax = home_price * property_tax_rate * years
    total_maintenance = home_price * maintenance_rate * years
    home_value = home_price * (1 + home_appreciation) ** years
    equity = home_value - loan  # simplified (ignores principal paid)
    total_buy_cost = total_mortgage + total_tax + total_maintenance - (home_value - home_price)

    # Renting costs over years
    total_rent = sum(monthly_rent * (1 + rent_increase_rate) ** y * 12 for y in range(years))
    # Down payment invested
    investment_gain = down_payment * ((1 + investment_return) ** years - 1)

    print(f"--- Buying ---")
    print(f"Total mortgage paid:  ${total_mortgage:,.0f}")
    print(f"Home value at year {years}: ${home_value:,.0f}")
    print(f"Net cost to buy:      ${total_buy_cost:,.0f}")
    print(f"\n--- Renting ---")
    print(f"Total rent paid:      ${total_rent:,.0f}")
    print(f"Down payment gain:    ${investment_gain:,.0f}")
    print(f"Net cost to rent:     ${total_rent - investment_gain:,.0f}")

rent_vs_buy(400000, 80000, 7.0, 30, 2000)