A cheaper month-one check is not a rent-vs-buy decision. Rent asks for one number. Owning asks for housing cash (P&I plus tax, insurance, and maintenance) every month, plus upfront costs, plus sale frictions, plus the opportunity cost of a down payment that could have stayed invested. This guide owns the monthly cash twin, a verified horizon strip, and the crossover year where buy net first beats rent under one honest sketch. Open the Rent vs Buy Calculator for the live strip; use Mortgage for a payment build and House Affordability when income gates come first.
What this guide owns
- Monthly cash twin: starting rent versus buy housing cash (not P&I alone).
- Horizon net: cash spent, equity after sale, and opportunity cost on the same stay length.
- Verified $400k seven-year-base twin with a 3 / 5 / 7 / 10 / 15 strip and ~year-6 crossover.
- Handoffs when the real question is affordability, refinance, or payment literacy.
It is not a refinance term-reset interest twin and not a closing-cost break-even clock.
If you are still asking “how much house can my income carry?” start with the PITI and DTI guide or the house affordability framework. Rent vs buy assumes you already have a price and a rent to compare.
Two scoreboards, one decision
Scoreboard A · Monthly cash
Rent side ≈ starting monthly rent Buy side ≈ P&I + property tax / 12 + insurance + maintenance Monthly gap ≈ buy housing cash − rent
Down payment and closing costs do not appear in the monthly twin. They hit at purchase. Opportunity cost on the down payment appears in the horizon net, not in month one.
Scoreboard B · Horizon net (same stay length)
Buy cash spent ≈ down + closing + housing cash × months Equity after sale ≈ sale proceeds after selling costs − remaining loan Opportunity cost ≈ growth you forgo by locking cash in the down payment Buy net ≈ cash spent + opportunity cost − equity after sale Rent net ≈ sum of rent with annual increases over the same years
Lower net is the sketch “winner” for that horizon. It is not a moral verdict and it is not a guarantee that appreciation, rent growth, or selling costs will match the inputs.
Lifestyle flexibility, commute, and whether you will actually stay still sit outside the spreadsheet. Use the math to bound the decision, not to replace judgment about tenure.
Verified twin: $400k, 20% down, $2,200 rent
Illustrative only. Matches the calculator’s seven-year base preset defaults. Confirm on the Rent vs Buy Calculator with your price, rent, and honest stay estimate.
Home price = $400,000 Down payment = $80,000 (20%) Loan = $320,000 @ 6.50%, 30 years Starting rent = $2,200 / mo Property tax = 1.2% of price / year Insurance + maint. = $150 + $150 / mo Rent growth = 3% / year Home appreciation = 3% / year Closing costs = 3% of price Selling costs = 6% of sale value Opportunity cost rate = 5% / year on the down payment
Monthly cash twin
| Side | Approx. monthly |
|---|---|
| Starting rent | $2,200 |
| Buy housing cash (P&I + tax + ins + maint) | ~$2,723 |
| Of which P&I | ~$2,023 |
| Monthly gap (buy cash higher) | ~$523 |
On month one, rent wins the checkbook. If you stop here, you never see that the horizon strip can flip.
Rerun P&I alone on the Mortgage Calculator if you need a payment build for a known price. Do not treat P&I as full housing cash when you compare to rent.
Horizon strip (same deal, different stay)
| Stay | Buy net (approx.) | Rent net (approx.) | Sketch winner |
|---|---|---|---|
| 3 years | ~$100,000 | ~$82,000 | Rent |
| 5 years | ~$141,000 | ~$140,000 | About flat |
| 7 years | ~$180,000 | ~$202,000 | Buy (−~$22k) |
| 10 years | ~$235,000 | ~$303,000 | Buy |
| 15 years | ~$315,000 | ~$491,000 | Buy |
Under these assumptions, buy net first beats rent around year 6 (crossover search 1–30). A forced move at year 3 turns the “owning builds equity” story into a rent win once closing and selling frictions dominate. A planned seven-year stay already favors buy on net in this sketch, even though month-one buy cash is ~$523 higher.
That strip is not a DTI stretch ladder and not a refinance keep/match/reset interest twin. It is tenure sensitivity: one deal, many stay lengths.
What moves the crossover
Levers that usually favor renting longer (push crossover later or erase it):
- Short planned stay with full selling costs.
- High opportunity cost on a large down payment.
- Low appreciation or flat prices at exit.
- Buy housing cash far above rent with thin rent growth.
Levers that usually favor buying sooner (pull crossover earlier):
- Faster rent growth (hot rental markets).
- Longer honest stay with equity after sale compounding.
- Lower selling costs or a planned exit that you will actually execute.
- Smaller monthly gap (or rent already above buy housing cash).
Hot-rent peel (illustrative): same style of sketch with higher rent ($2,800), slightly higher price ($450k), and 5% rent growth often pulls crossover toward year 4 on the calculator’s hot-rent preset. Month-one buy cash can still be higher while the horizon flips earlier. Do not import that peel into a soft rental market.
Optimistic appreciation with tiny selling costs flatters buying. High opp cost on a huge down payment flatters renting. Stress the levers that hurt your preferred story before you celebrate.
Opportunity cost is not optional math
The down payment is capital. If you rent, that cash (and often the monthly gap when rent is cheaper) can stay invested. The tool sketches opportunity cost as forgone growth on the down payment while you own. It is not a promise of market returns and not advice to invest. It is a reminder that “equity” is not free: you tied up cash to get it.
If you ignore opportunity cost, buying looks better than the sketch. If you assume unrealistically high opp rates, renting looks better. Use a conservative band and keep it visible next to appreciation assumptions.
How this differs from nearby housing guides
| Question | Better page |
|---|---|
| Monthly cash vs horizon net for a price and rent | This guide + Rent vs Buy Calculator |
| Income → DTI budget → max price → leftover | PITI and DTI |
| Listing stack, DTI comfort, +1% rate stress | House affordability framework |
| Refinance costs ÷ monthly P&I savings | Refinance break-even |
| Keep / match / reset remaining interest | Refinance term-reset trap |
| P&I input mistakes on a known loan | Mortgage calculator mistakes |
Rent vs buy is tenure economics between two paths. Affordability is income vs payment fit. Refinance guides are about swapping an existing loan.
Practical checklist before you treat a quote as a decision
- Write your honest stay (3 / 7 / 15), not the longest horizon that flatters buying.
- Build buy housing cash (P&I + tax + insurance + maintenance), not P&I alone.
- Run the Rent vs Buy strip at 3, 5, 7, 10, and 15 years.
- Note the crossover year and whether your stay sits before or after it.
- Stress lower appreciation and higher selling costs once.
- If income is the blocker, stop and run House Affordability first.
- Keep assumptions written so you cannot rewrite history after the market moves.
Couples should negotiate stay length first. Disagreement about 3 vs 10 years usually matters more than a 0.25% rate tweak on this page.
Common failure modes
- Comparing rent to P&I only while tax, insurance, and maintenance sit off-stage.
- Assuming a 30-year stay when the job moves every three years.
- Ignoring selling costs on short holds.
- Forgetting opportunity cost on a large down payment.
- Treating month-one “rent is cheaper” as the full answer.
- Using this sketch instead of a detailed payment build when you already own the listing math.
- Skipping affordability and stretching into a house the horizon sketch “likes.”
When this sketch is not enough
- Markets with large HOA specials, flood insurance, or condo litigation risk.
- Capital-gains tax, primary-residence exclusions, and itemized deduction changes.
- PMI details when down payment is under 20% (model housing cash carefully).
- New construction incentives, seller credits, and temporary buydowns that expire mid-horizon.
- Households that need to move for care, immigration, or visa timelines with hard dates.
For purchasing-power literacy on dollar totals, pair with the Inflation Calculator. For investment-side context on capital you might keep liquid while renting, see the Investment Calculator as education, not as a housing endorsement.
FAQ
Is buying always better if you stay long enough?
Not automatically. Long stays often help the buy path in sketches like this one, but only if the payment is sustainable and maintenance, taxes, insurance, and exit costs stay in the model. A long stay with an unaffordable stack is still a bad buy.
What is the most important input?
Honest time horizon. If you might move soon, transaction costs often dominate. If you will stay through and past crossover, monthly gap matters less than net cost.
Why does buy cash look higher than rent in the twin but buy still win at seven years?
Because horizon net credits equity after sale and accumulates rising rent on the rent path. Month-one cash and multi-year net answer different questions.
How should I estimate maintenance?
Many sketches use a flat monthly reserve (here $150 on a $400k home) or about 1%–3% of value per year as a planning band. Older homes and harsh climates can run higher. Replace the placeholder with local quotes when stakes are high.
How should I treat home price appreciation?
Use a conservative range. The decision should still make sense if appreciation is modest. Do not require heroic price growth to justify a purchase you cannot afford on cash flow.
Does a lower monthly gap mean I should buy?
Not by itself. A small gap with a two-year stay can still lose to selling costs. A larger gap with a fifteen-year stay can still favor buy on net. Read the strip.
How is this different from refinance break-even?
Refinance break-even asks when payment savings repay closing costs on an existing loan swap. Rent vs buy asks whether renting or owning has lower all-in net cost over a stay. Related math family, different decision.
Bottom line
Run both scoreboards. The monthly twin tells you whether next month’s cash fits. The horizon strip tells you whether that fit survives the stay you actually expect. On the verified $400k sketch, rent wins month one and year three; the paths are about flat at five years; buy pulls ahead by seven with crossover near year six. Paste your numbers into the Rent vs Buy Calculator, stress the levers that hurt your preferred story, and only then treat the verdict as planning input, not destiny.