How the Rent vs Buy Calculator Finds the Break-Even Year
The calculator reframes "rent or buy?" as "after how many years does buying become cheaper?" and answers it by tracking the cumulative net cost of each path year by year. On the BUY side it sums the cash spent — down payment, closing costs, mortgage principal & interest (from the shared reducing-balance loan engine), property tax, home insurance, maintenance and HOA, minus any optional tax benefit — and then subtracts the proceeds you would walk away with on a sale: the home value, grown by appreciation, times one minus the selling-cost percent, minus the remaining loan balance. That net figure is cash spent minus the equity and appreciation you keep. On the RENT side it sums rent (grown by rent growth each year) plus renter’s insurance, then subtracts the after-tax gain on the money a renter invests instead of buying. The break-even year is the first year buying’s net cost falls below renting’s. Everything is a pure, unit-tested function that updates live as you type.
- Answer is a break-even year, not a monthly mortgage-vs-rent compare
- Net cost of buying = cash spent − (home value − selling costs − loan balance)
- Net cost of renting = rent paid − after-tax investment gain
- Mortgage reuses the shared reducing-balance loan engine
- Break-even = first year buying’s net cost drops below renting’s
