Cumulative Net Cost Over Time
Lower is better. Negative values mean you came out ahead financially.
Methodology.
Both the buyer and renter begin with the same capital (down payment + closing costs).
The renter invests that capital at the specified return rate, plus any monthly savings when
renting costs less than buying (if buying is more expensive per month, the renter invests the
difference; if renting is more expensive, the renter draws from the portfolio).
Net cost to buy = all cash paid out (down payment, closing costs, full mortgage
payments, property taxes, maintenance) minus net sale proceeds (home value × (1 − selling rate)
− remaining mortgage balance). Property taxes and maintenance are recalculated each year
against the current appreciated home value.
Net cost to rent = cumulative rent paid, minus investment portfolio gains above
the initial capital deployed. When net cost to buy < net cost to rent, owning has become the
more efficient use of capital over the chosen horizon.