Every parent, financial adviser, and personal-finance blog will tell you the same thing: put 20% down. Avoid PMI. Don't be one of those irresponsible people buying with a small down payment. It sounds like received wisdom. It is also, at 2026 numbers, wrong at least half the time.
The 20%-down default was a rule for a world with 3% mortgage rates and 15% annual home price appreciation. In that world, having your down payment sit in cash for two years while you saved another $50,000 wasn't very expensive, and the PMI you avoided by hitting 20% was a real recurring cost. That's not this world.
Here's the actual math, at a 4-year stay and a 15-year stay, honestly comparing what happens if you buy with 5% down now versus waiting to buy with 20% down.
The frame: what you're really trading
There are three moving pieces when you compare 5% down now against 20% down later:
- PMI cost. At 5% down you pay PMI until your LTV falls below 78%. On a $400k house at 780 credit, that's roughly $80/month for about 10 years — total lifetime cost around $8,000-$10,000 depending on appreciation. Non-trivial but not catastrophic. See the PMI piece for the full credit-score sensitivity.
- Appreciation you capture (or don't). If you buy now at $400k and prices rise 3% per year, in 2 years the house is worth $424,800. If you're the buyer, that $24,800 is your equity. If you wait, that's $24,800 you're paying to the seller instead of paying to yourself.
- Invested-difference return. At 5% down you invest the $60k you didn't put into the house. At 20% down you don't — that $60k is dead equity. So the 5%-down buyer has an alternative return advantage on the invested difference.
The 20%-down argument boils down to "PMI is real, and appreciation is uncertain." The 5%-down argument boils down to "appreciation is highly likely to exceed PMI, and my alternative portfolio return is also real." Both are true. The honest question is which effect is bigger, at what stay length.
The setup
Same house both scenarios: $400,000 purchase, US-average state (1% property tax), 30-year fixed at 6.72% (Freddie Mac PMMS July 2026), 780 credit score, 3% nominal home price appreciation (S&P/Case-Shiller long-run), 3% rent inflation, US-median rent of $2,320/month for the equivalent housing.
The 5%-down buyer buys today. The 20%-down buyer needs to save an additional $60,000 to make up the gap. At a $2,000/month savings rate (roughly what someone in the market for a first house at this price point can save above rent), that takes 30 months (2.5 years). During those 30 months the 20%-down buyer is renting and the house is appreciating.
We hold the invested-difference return at 5% real (60/40 baseline; see the alternative-return piece) unless the sensitivity table says otherwise.
Scenario 1: 4-year stay
You buy, stay 4 years, sell.
5% down buyer, buys today at $400,000:
- Down payment: $20,000
- Loan: $380,000 at 6.72% → $2,458/month P&I
- Property tax: $333/month (year 1, drifting to $377 by year 4)
- Insurance: $192/month, drifting to $233 by year 4
- PMI: $79/month for all 4 years (LTV doesn't drop below 78% in this window)
- Maintenance: $333/month
- Total year-1 monthly cost of ownership: $3,395 (rising with tax + insurance drift)
- Sale in year 4: house is worth $400k × 1.03^4 = $450,200
- Loan balance at year 4: ~$362,000
- Selling costs at 6.5%: $29,263
- Net equity at sale: $450,200 − $362,000 − $29,263 = $58,937
- Cash out: $58,937 − $20,000 initial down payment = +$38,937, of which ~$14,000 came from paying down loan principal + $24,900 from appreciation.
20%-down buyer waits 30 months, then buys at $400,000 × 1.03^2.5 = $431,000:
- Delay: rents for 30 months at $2,320/month × 3% inflation → $71,200 total rent paid
- Invested the $20,000 they already had for 2.5 years at 5% real: → $22,600 (adds $2,600)
- Additional savings of $2,000/month for 30 months at 5% real: → $63,900 total (saved $60,000 principal, gained $3,900 return)
- Buys the same house at $431,000 with 20% down = $86,200
- Loan: $344,800 at 6.72% (assume same rate, though it could differ) → $2,232/month P&I
- No PMI. Property tax higher because assessed value is higher.
- Sells at year 4 of ownership (year 6.5 from start). House value at that point: $431,000 × 1.03^4 = $485,100
- Loan balance at year 4 of ownership: ~$328,500
- Selling costs at 6.5%: $31,540
- Net equity at sale: $485,100 − $328,500 − $31,540 = $125,060
- Total ownership cash-out: $125,060 − $86,200 down = +$38,860
- But subtract the $71,200 rent paid during delay and $37,400 saved-not-invested opportunity cost.
Net-net at year 4-of-ownership (6.5 years from decision):
- 5% down buyer: owns 4 years' worth of house equity + spent 4 years' worth of ownership expenses. Ends with $38,937 above initial down payment.
- 20% down buyer: owns 4 years' worth of house equity from a higher basis + spent 6.5 years' worth of housing (2.5 renting + 4 owning). Nets very close to the same equity accretion, but paid $71,200 in rent during the delay and now sits 2.5 years later on the same career trajectory.
Honest conclusion at 4-year hold: the 5%-down buyer is ahead by roughly $30,000–$45,000 compared to the 20%-down buyer, most of which comes from not paying $71k of rent during the 2.5-year delay. PMI cost of ~$3,800 over 4 years is a rounding error next to the delay-rent bill. Buying at 5% down wins clearly at short stay lengths.
But wait — 4-year stays are the case where buying itself often loses to renting because of the closing-cost drag. Both of these scenarios probably underperform someone who just rented the whole 4 years. That's a separate question (break-even year piece). The comparison here is 5%-down-buy vs 20%-down-buy, assuming you've already decided to buy.
Scenario 2: 15-year stay
Now stretch the timeline. The stay is long enough for PMI to have dropped off (LTV crosses 78% around month 122 in the 5%-down scenario, so PMI drops in year 11 either voluntarily or automatically). Property values compound. Rent-during-delay compounds too.
5% down buyer at year 15:
- 10 years of PMI at ~$80/month → $9,600 total (drops off in year 11)
- 15 years of principal paydown → loan balance ~$296,000
- House value at year 15: $400k × 1.03^15 = $623,100
- Sells at year 15. Selling costs 6.5%: $40,500
- Net equity: $623,100 − $296,000 − $40,500 = $286,600
- Cash-out above initial $20k: +$266,600
- Meanwhile the alternative was: the $60k you didn't put into the house sat invested at 5% real for 15 years → $124,700 (adds $64,700 in return)
- Net position: $266,600 (from house) + $64,700 (from invested difference) = ~$331,300 wealth above initial deposit
20% down buyer at year 15:
- Delayed 2.5 years, so year 15 = year 12.5 of ownership
- Rented for 2.5 years: $71,200 rent paid (never recovered)
- Bought at $431,000 with $86,200 down
- 12.5 years of no PMI
- Loan balance at year 12.5: ~$291,300
- House value at year 12.5: $431,000 × 1.03^12.5 = $625,700
- Sells now. Selling costs 6.5%: $40,670
- Net equity: $625,700 − $291,300 − $40,670 = $293,730
- Cash-out above initial ~$86k: +$207,530
- No invested-difference return (all cash went to down payment)
- Net position: ~$207,530 wealth above initial deposit, but paid $71,200 in rent during delay
Compare final wealth at the same absolute timeline (15 years from decision date):
- 5%-down: ~$331,300 total wealth increase from housing + alternative
- 20%-down: ~$207,530 from housing, minus $71,200 rent-during-delay = net ~$136,330 at the same absolute point
5%-down wins by roughly $195,000 over the 15-year window at these assumptions. PMI cost of $9,600 was overwhelmed by 3 things: appreciation on a house bought earlier and cheaper, compounding on the invested difference, and 30 months of not paying rent during the "save more" phase.
Where the answer flips: the sensitivity that matters
The 5%-down verdict at both stay lengths depends on three assumptions. Change them and the story changes.
| Change | Effect on 5%-vs-20% verdict |
|---|---|
| Home price appreciation drops to 1% nominal | 20%-down closes most of the gap at 15 years; still loses at 4 years |
| Home price appreciation zero real (nominal = inflation) | 20%-down catches up by year ~15; wins on any timeline shorter |
| Alternative return drops to 2% real (holding cash) | 20%-down looks better; PMI + tax on higher basis still doesn't kill 5%-down |
| Alternative return climbs to 8% real (aggressive equities) | 5%-down wins by even more |
| Mortgage rate at 5%-down bump of +50bps (some lenders price small down higher) | Narrows the gap by ~$8k over 15 years |
| Credit score 680 (PMI ~1% instead of 0.25%) | PMI cost roughly quadruples; adds ~$25k over 10 years to 5%-down side. Still 5%-down wins on the median, but closer. |
| No rent while saving (living with family for free) | 20%-down catches up substantially — the "delay rent" line disappears |
| Longer wait to hit 20% (say 5 years instead of 2.5) | 5%-down wins by more; 20%-down keeps paying delay-rent and missing appreciation |
The two conditions under which 20%-down actually wins on the median case are: (a) home price appreciation is materially negative in real terms during the delay, or (b) you can live rent-free while saving. Neither is the base case.
Two more caveats worth knowing
Caveat 1: house-selection quality. Buying with 5% down often means buying a slightly cheaper house than the buyer intended, because lenders tighten the DTI ratios on low-down-payment loans. The above math assumes both buyers land on the same house. If the 5%-down constraint forces you to a $340k house instead of your target $400k, the appreciation math changes proportionally — you're capturing 3% on a smaller base. Adjust accordingly.
Caveat 2: risk during the first 3 years. At 5% down, you have very little equity. A 5% market pullback puts you underwater. A job loss and forced sale in year 2 could turn into a real cash loss. This is a real risk, not a math one. If your income is not stable, or you're in a metro with historically volatile prices, having a bigger equity cushion is worth something the median-case math doesn't price.
The honest answer
At 2026 mortgage rates (6.72% for a 30-year fixed) and 3% nominal appreciation:
- If you can buy today at 5% down without wrecking your emergency fund, do it. The delay-rent cost and missed appreciation are usually bigger than the PMI you avoid.
- Wait for 20% only if: your credit score is under 660 (PMI runs 1%+ of loan/year), your income is unstable, you can live rent-free while saving, or you genuinely believe home prices will drop 5%+ in real terms in your metro during the delay.
- Don't wait for 20% just because your parents said so. They were saving in an era of 3% mortgages and 15% appreciation. In that world, waiting was cheap. Today it's expensive.
The 20%-down rule is not wrong. It's a rule that made a lot of sense in a specific rate and appreciation regime. The regime changed. The rule didn't. That's how outdated defaults survive.
Ready to run the 5% vs 20% comparison on your specific numbers? Try the rent-vs-buy calculator → — down payment is a top-level input, PMI drops out automatically at the correct LTV, and the sensitivity table shows exactly which assumption tips the answer.