Why “It Depends” Is the Honest Answer — and What It Depends On
Popular personal finance advice tends to assert that buying is always better (“building equity”) or that renting is always smarter (“flexibility, no maintenance costs”). Both framings are incomplete. Whether renting or buying is financially better depends on at least six quantifiable variables: the home price, the mortgage rate, the planning horizon, local rent levels, the expected investment return on money not committed to a down payment, and how quickly the home appreciates. Changing any one of these can reverse the conclusion.
The rent-vs-buy comparison is not a values question about homeownership — it is a discounted-cash-flow problem. This guide explains the math behind that comparison, walks through a concrete worked example, and shows what the inputs and outputs of the calculator actually represent.
The Two Costs Being Compared
The comparison measures cumulative net cost on both sides over a planning horizon — the number of years a person expects to stay in the same housing situation.
The buy side accumulates: closing costs paid upfront, mortgage interest (the non-equity portion of each payment), property taxes, homeowner’s insurance, maintenance and repairs, HOA fees if applicable, and selling costs at exit. Against these outflows, the buyer gains home equity (the market value of the home minus the remaining loan balance), and that equity is realized as cash when the home is sold. The net buy cost = all cash paid in minus net sale proceeds at the end of the horizon.
The rent side accumulates: total rent paid over the horizon, plus renter’s insurance. However, the renter has NOT committed the down payment and closing costs to real estate — those funds are available to invest. The investment growth on that capital reduces the renter’s effective cost. This subtraction — sometimes called the opportunity cost offset — is one of the most commonly omitted factors in informal rent-vs-buy comparisons.
Omitting the opportunity cost makes buying look cheaper than it often is, particularly in the early years of homeownership when the down payment could have been growing in an investment account.
How the Calculator Builds Each Side of the Comparison
Buy Leg: Year-by-Year Simulation
The calculator simulates the buy scenario one month at a time, tracking:
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Mortgage amortization: each payment splits between interest (charged on the remaining loan balance) and principal (which reduces the balance). Early payments are interest-heavy; later payments are principal-heavy — the same amortization effect described in the mortgage payments guide.
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Carrying costs: property taxes (assessed against the home’s current value as it appreciates), homeowner’s insurance, maintenance, HOA fees, and PMI if the down payment was below 20%.
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PMI removal: when the outstanding loan balance falls below 80% of the original purchase price, PMI drops automatically — month by month, not at an arbitrary future date.
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Home equity: at any point in the horizon, equity = home value − outstanding loan balance. Home value grows annually at the appreciation rate.
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Selling costs: when the simulation reaches the planning horizon, the calculator deducts selling costs (realtor commissions and transfer taxes, commonly 6–7% of sale price) from the sale proceeds. Without this deduction, short-horizon buying scenarios look artificially favorable.
The net buy cost at the planning horizon is: closing costs + all carrying costs paid + total mortgage interest − home equity realized + selling costs.
Rent Leg: Cumulative Cash Paid Less Investment Growth
The rent side accumulates rent and renter’s insurance over the horizon. Annual rent grows at a specified rate (the default 3% matches typical recent US rent inflation). Against this, the calculator subtracts the investment growth on the down payment and closing costs invested at the specified return rate:
Rent net cost = total rent paid − (down payment + closing costs) × ((1 + return rate)^N − 1)The subtraction reduces the renter’s effective cost because those funds are working in the market rather than sitting in a house. A higher investment return rate makes renting look cheaper; a lower return makes buying look cheaper — which is why this input is worth scrutinizing.
The calculator uses a real (inflation-adjusted) return rate, consistent with how the FIRE calculator on this site handles long-term investment projections. The default 5% reflects a common estimate for long-run US equity real returns.
Worked Example: $450,000 Home Over 10 Years
A practical worked example using concrete, nationally representative numbers for a US homebuyer in 2026:
Inputs:
- Home price: $450,000
- Down payment: 20% ($90,000)
- Mortgage rate: 7.0% / 30-year term
- Closing costs: 3% ($13,500)
- Property tax: 1.1% of home value annually
- Homeowner’s insurance: 0.5% of purchase price annually
- Maintenance: 1.0% of purchase price annually
- Home appreciation: 3% per year
- Selling costs: 7% of sale price at exit
- Current monthly rent: $2,500
- Annual rent growth: 3%
- Renter’s insurance: $15/month
- Investment return on down payment: 5% real
- Planning horizon: 10 years
Buy side results:
- Loan amount: $360,000 (home price minus 20% down payment)
- Monthly mortgage payment (P&I): $2,395.09
- Home value after 10 years at 3% annual appreciation: $604,762
- Remaining loan balance at year 10: approximately $308,924
- Home equity at horizon: $295,838
- Selling costs at horizon (7% of $604,762): $42,333
- Net sale proceeds: $253,505
Rent side results:
- The $103,500 committed to down payment + closing costs, invested at 5% real for 10 years, grows by approximately $65,091 — this offset reduces the renter’s effective cost.
Verdict at 10 years: Buying is cheaper by approximately $18,973, with a break-even year of 9. Before year 9, renting is cheaper on a cumulative basis; from year 9 onward, the cumulative cost of buying falls below the cumulative cost of renting.
At a 5-year horizon with the same inputs, renting is cheaper by approximately $29,374 — the break-even has not been reached yet, and the selling costs (7% of appreciated home value) still outweigh the equity built in five years.
How to Use the Rent vs. Buy Calculator
Planning horizon is the most important input. If a buyer plans to relocate in three years, even favorable mortgage terms are unlikely to overcome the transaction costs (closing costs plus selling costs, typically 10–11% of price combined). Longer horizons give appreciation and principal paydown time to build equity that exceeds those fixed costs.
Home appreciation rate is the single most sensitive assumption in the buy leg. At 4% annual appreciation instead of 3%, the 10-year home value in the worked example above rises by more than $25,000, directly improving the buy outcome. Use conservative local estimates from market data rather than recent post-pandemic appreciation rates, which were anomalously high.
Investment return rate is the assumption most often ignored in informal rent-vs-buy comparisons. A renter who does NOT invest the down payment savings cannot claim the opportunity cost offset — if the money is spent rather than invested, the rent leg costs more than the calculator’s baseline shows. Conversely, investors who consistently earn above-market returns will find renting more financially attractive at the same home price.
Selling costs (7% default) are frequently underestimated. Realtor commissions alone often total 5–6% of the sale price; transfer taxes add 0.5–2% depending on the state. These are deducted from sale proceeds at exit, and because they apply to the appreciated price rather than the purchase price, they grow with the home’s value. Enter 0% only if there is no realistic expectation of selling.
PMI applies automatically when the down payment is less than 20%. The calculator tracks PMI removal in real time — it drops when the loan balance falls to 80% of the original purchase price, which may happen earlier than a standard 80% amortization timeline when home appreciation is included.
The Break-Even Year: What It Measures
The break-even year is the first year in which the cumulative net cost of buying falls below the cumulative net cost of renting. Before that year, renting is cheaper on a total-cost basis; from that year onward, buying is.
The break-even year is sensitive to three variables: planning horizon, appreciation rate, and investment return rate. Higher appreciation shortens the break-even (equity builds faster, reducing net buy cost). Higher investment return lengthens it (the renter’s offset grows faster, making renting cheaper for longer). A shorter planning horizon effectively truncates the simulation before the break-even can occur.
The calculator searches for break-even up to 30 years. If no break-even occurs within 30 years at the specified inputs, it reports explicitly that buying never becomes cheaper over the full range — a result that can occur when rent is very low relative to the home price, when the investment return rate is high, or when selling costs are substantial.
Frequently Asked Questions
Does the calculator include the mortgage interest deduction? No. The mortgage interest deduction is available only to taxpayers who itemize deductions, and since the 2017 Tax Cuts and Jobs Act roughly doubled the standard deduction, the majority of US taxpayers no longer itemize — making the deduction unavailable in practice. Including it would overstate the tax benefit for most users. Borrowers in high-income situations who do itemize should factor in the after-tax mortgage cost separately.
How does home appreciation affect the comparison? Appreciation improves the buy side in two ways: it increases the home value at exit (raising net sale proceeds) and it accelerates PMI removal (the loan balance falls below 80% of the appreciated home value faster). At low appreciation rates (0–2%), the buy side is harder to justify over short horizons because equity builds slowly while selling costs remain fixed. At high appreciation rates (5%+), buying often dominates even at relatively short horizons — but forecasting appreciation reliably over 10 years is difficult, and recent post-pandemic appreciation rates are not a reliable baseline for projections.
What if I plan to rent out the property eventually? The calculator models owner-occupancy only — it does not include rental income, depreciation deductions, or the higher insurance and maintenance costs of investment properties. Rental income can dramatically change the economics of buying, but it also introduces landlord responsibilities, vacancy risk, and tax complexity that are outside the scope of this tool.
How do closing costs affect the break-even year? Closing costs are a fixed upfront buy-side expense. A 3% closing cost on a $450,000 home is $13,500 paid at purchase — the buyer must accumulate enough equity and appreciation to recoup that, plus the selling costs at exit, before the cumulative cost of buying falls below the cumulative cost of renting. Larger closing costs push the break-even year later; smaller closing costs (or seller-paid closing costs negotiated in the purchase) pull it earlier.
How does the rent growth rate affect the comparison? Higher rent growth makes renting more expensive over time (each year’s rent is higher than the previous year’s), which favors buying. Lower rent growth leaves more money in the renter’s budget, which narrows the gap. Rent growth at or below home appreciation does not automatically favor buying because the down payment opportunity cost and selling costs also scale with home value.