The Rent vs Buy Question Everyone Gets Wrong

Type “rent vs buy calculator” into Google and you’ll find dozens of tools that boil the decision down to one comparison: mortgage payment versus rent payment. If the mortgage is lower, buy. If rent is lower, rent. Simple, clean, and missing about half the real picture.

Here’s what’s interesting — homeownership has costs that never show up on a mortgage statement. Maintenance alone typically runs 1-2% of your home’s value every single year (a $400,000 house means $4,000-$8,000 annually just keeping things from breaking). Add property tax, insurance, and the 6-8% in agent commissions and closing costs you’ll pay when you eventually sell, and the math shifts substantially from what a bare mortgage-vs-rent comparison shows — this calculator’s own model lands on roughly 7% as its working assumption for that selling cost, applied to the home’s projected future value at the end of whatever timeframe you select.

The Piece Almost Nobody Calculates: Opportunity Cost

A 20% down payment on a $400,000 home is $80,000. That money has to come from somewhere, and once it’s in a house, it’s not earning anything else. If you rented instead and invested that $80,000 in a simple index fund, historical long-run returns (the S&P 500 has averaged roughly 7% annually after inflation over many decades) would have it compounding the entire time you’re renting.

This calculator treats that down payment as an investment that grows in the renting scenario, then compares it against the equity you’d build in the buying scenario. That’s the actual apples-to-apples comparison — not “mortgage vs rent,” but “what happens to my money under each path.”

Why the Break-Even Year Matters More Than the Monthly Payment

Buying almost always starts out financially worse than renting, because of upfront closing costs and the fact that early mortgage payments go mostly toward interest, not equity. But here’s the thing — rent tends to rise every year, while a fixed-rate mortgage payment doesn’t. Eventually the lines cross. That crossing point is the break-even year, and it’s a far more useful number than comparing today’s payments side by side.

If you’re planning to move again in 2-3 years, a break-even year of 8 is a strong signal to keep renting. If you’re putting down roots for a decade or more, the same number tells a very different story. That said, a crossing point isn’t guaranteed to exist within any normal timeframe — in scenarios with weak home appreciation or a strong investment return on the down payment, renting and investing the difference can stay ahead of buying for decades rather than losing out eventually, so it’s worth treating “buying wins if you wait long enough” as a tendency, not a rule.

Example Calculation

What Changes the Answer the Most

Three inputs swing the result more than anything else. Mortgage rate matters enormously — a 2-point difference in rate can shift the break-even year by 3-5 years on its own. Home appreciation is the second lever; in flat or declining markets, buying’s advantage shrinks or disappears. And the investment return assumption for the renting scenario matters too — assume a higher market return and renting looks more competitive for longer, since the down payment grows faster on the sidelines.

None of these are predictable with certainty, which is exactly why running a few different scenarios (try the sliders with slightly higher and lower rates) gives a more honest picture than trusting a single number — small changes to these assumptions can shift the break-even point by several years, so the year shown is a directional estimate, not a precise prediction.

What This Calculator Doesn’t Capture

This is a financial model, not a life-decision model. It doesn’t weigh the stability of owning, the flexibility of renting, the cost and hassle of moving, or the value of being able to renovate a space that’s yours. Plenty of people buy for reasons that have nothing to do with which option wins on a spreadsheet — that’s a legitimate choice the math here isn’t trying to override.