There's a shortcut that cuts through most rent-vs-buy debates in about thirty seconds: take the home price, multiply by 5%, divide by 12. If your rent is below that number, keep renting. If it's above, buying starts to look genuinely competitive. It won't settle the argument entirely, but it beats staring at a mortgage payment and a rent check side by side and calling that a comparison.
The 5% rule, worked through
Take a $400,000 house. Five percent of that is $20,000 a year, or about $1,667 a month. That figure is meant to represent the true annual cost of ownership — roughly 1% in property tax, 1% in maintenance, and 3% as the effective cost of the capital tied up in the home, whether that's mortgage interest or the return you're giving up by not investing the down payment elsewhere. If comparable rent nearby runs below $1,667, renting is likely the better financial move. Above it, buying starts pulling ahead. The rule holds up reasonably well — researchers estimate roughly 80-85% accuracy across markets — but it leans on assumptions (moderate appreciation, a 20%+ down payment, staying put 5+ years) that don't hold everywhere.
What the mortgage payment alone doesn't show you
Property tax, homeowners insurance, maintenance (commonly budgeted at 1-2% of home value a year), and — under a 20% down payment — private mortgage insurance all stack on top of principal and interest. Add the upfront cash: down payment plus closing costs, money renting simply doesn't demand.
What renting never gives you back
Every mortgage payment includes a principal slice that becomes equity — money that comes home to you, minus selling costs, whenever you eventually sell. Rent is different: the entire payment disappears, permanently, with nothing returned. Stretched over a long enough holding period, this is usually the single biggest argument in favor of buying, assuming the property at least holds its value.
Time horizon changes the entire answer
Buying only pays off once you've stayed long enough to absorb the transaction costs on both ends — closing costs going in, agent commissions coming out, commonly 2-5% and 6-10% of the price respectively. Someone likely to move within two or three years usually comes out ahead renting, even in a scenario where the long-term math clearly favors buying.
The opportunity cost cuts both directions
Money locked into a down payment could otherwise be invested — a real cost of buying that's easy to forget about. But the flip side matters too: if renting "saves" money that then just evaporates into lifestyle spending instead of actually getting invested, that theoretical advantage never materializes in real life.
Beyond the spreadsheet
Stability and control over your own space carry real value that doesn't show up in any of this math, just as renting's flexibility and freedom from maintenance responsibility genuinely matter to plenty of people. The financially "optimal" answer on paper isn't automatically the right answer for someone's actual life.
Model your specific numbers with the Mortgage Calculator, and see how a down payment invested instead could grow with the Compound Interest Calculator.
A few things people actually ask
How accurate is the 5% rule, really?
Researchers estimate roughly 80-85% accuracy across diverse markets, though it works best with moderate appreciation, a 20%+ down payment, and staying put 5+ years — and it's noticeably less reliable outside those conditions.
How long do I need to stay in a home for buying to pay off?
Long enough to absorb transaction costs on both ends — commonly cited as 5+ years, since closing costs (2-5% going in) and selling costs (6-10% going out) eat into any equity gain if you move too soon.
Does the money "saved" by renting actually help me if I don't invest it?
No — if the difference between rent and a mortgage payment just gets absorbed into everyday spending instead of being invested, the theoretical financial advantage of renting never actually materializes.