Personal finance media treats private mortgage insurance like a small pox. Wait until you have 20% down, the standard advice goes, or you’ll throw away thousands on PMI. The math behind that advice is incomplete in ways that cost real buyers real money. PMI is annoying, but for many borrowers in many markets, paying it is cheaper than waiting.
What PMI actually costs
PMI typically runs 0.3% to 1.5% of the loan amount per year, with most borrowers landing around 0.5% to 1%. On a $400,000 loan, that’s $2,000 to $4,000 a year. It comes off automatically when your loan-to-value ratio reaches 78%, and you can request removal at 80%. So the actual cost is a few thousand dollars a year for a few years — not the lifetime sentence the standard advice implies.
The advice to wait for 20% asks you to compare paying PMI now against paying nothing later. That’s not the right comparison. The right comparison is paying PMI now against paying the housing market’s appreciation later — and against paying market rent in the meantime.
The opportunity cost of waiting
Saving an additional 10% down payment on a $500,000 home means saving $50,000. At a household savings rate of $1,000 a month, that’s just over four years. In four years, in most American markets over the last twenty, home prices rose by 20% to 40%. The same house now costs $600,000 to $700,000, and 20% of that is $120,000 to $140,000 — significantly more than the saver was originally trying to accumulate.
Add in four years of rent — say $24,000 a year, or $96,000 over the period — and the cost of waiting balloons. The PMI you would have paid by buying earlier is a few thousand dollars annually for a few years. The market appreciation and rent you paid by waiting is often a hundred thousand or more.
When PMI is genuinely a bad deal
There are scenarios where waiting to hit 20% makes sense. In a flat or declining housing market, the appreciation argument disappears. If you’re buying at the top of your budget and PMI puts you over what you can comfortably afford, the additional cushion from a larger down payment matters. If you’re not sure you’ll stay in the home five years, transaction costs eat any savings.
The honest version of the advice is conditional. In appreciating markets, with stable income, and a multi-year time horizon, putting 5–10% down and paying PMI is usually mathematically superior to waiting. In flat markets, on a stretched budget, with uncertain plans, the standard advice holds up better.
The takeaway
PMI is not free, and the personal finance instinct to minimize unnecessary fees is reasonable. But the cost of PMI is bounded and short. The cost of being out of the housing market in an appreciating environment is open-ended and growing. The right framing is not “avoid PMI at all costs” but “what’s the cheapest way into the home I want?” — and PMI is often part of that answer.
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