Piggyback loan vs PMI: the credit score that changes the math

You've saved $35,000. You're putting 10% down on a $350k home. And now your lender mentions something called a piggyback loan -- take an 80% first mortgage, a 10% second mortgage, skip the PMI entirely. It sounds cleaner than paying $150 a month for insurance that protects the bank, not you. But at current second mortgage rates of 8.5%, the math isn't what it used to be. Whether the piggyback actually saves you money comes down to one number: your credit score.

The short answer is this: if your score is above 700, take the conventional loan with PMI. If it's below 680, the piggyback almost certainly wins. Between 680 and 700, you're in a genuine toss-up that depends on how long you plan to stay. Here's the full breakdown at today's 6.47% rates (Freddie Mac PMMS, June 18 2026).

What the piggyback loan actually costs

Let's use a real purchase: $350,000 home, $35,000 down (10%), two loans. The first covers 80% of the purchase price ($280,000). The second covers 10% ($35,000). You walk in with 10% down and no PMI, because the first lender sees only 80% LTV.

At 6.47% on the $280,000 first mortgage, your principal and interest payment is $1,764/month. The second mortgage -- typically offered as a home equity loan or second lien at roughly 8.5% on a 10-year term -- adds $434/month. Total piggyback payment: $2,198/month.

That $434 comes from the math on a 10-year fully amortizing loan: $35,000 at 8.5% runs a payment factor of $12.40 per thousand, so $35k produces $434. It's not cheap, because the lender on that second loan takes more risk -- they're behind the first mortgage in the event of foreclosure. They price that risk into the rate.

Now compare the conventional alternative. On a $315,000 loan (same 10% down, single first mortgage) at 6.47%, your P&I is $1,985/month. Add PMI, and the total depends on your credit score.

The PMI math by credit tier

Private mortgage insurance pricing isn't flat. Insurers like MGIC and Arch price it by credit score and LTV. At 90% LTV, the annual rate ranges from roughly 0.28% for a 760+ credit score to 1.65% for a 640-659 score. That translates directly into your monthly payment.

Here's the full comparison on a $350k purchase with 10% down at 6.47% rates (conventional P&I: $1,985/month; piggyback total: $2,198/month):

PMI rates based on typical MGIC/Arch pricing at 90% LTV, June 2026. P&I on first mortgage ($315k or $280k) calculated at 6.47%, 30-year fixed (Freddie Mac PMMS, June 18 2026). Second mortgage at 8.5%, 10-year term. Note: credit scores below 700 also face higher first mortgage rates via Fannie Mae LLPAs, which widens the piggyback advantage further -- this table isolates the PMI effect only.

The break-even PMI rate -- where both options cost exactly the same -- is $213/month, or about 0.81%/year on the loan balance. That corresponds to roughly a 695 credit score. So if you're a 699, you're essentially indifferent. The conventional PMI wins on a monthly basis but barely.

If your score is sitting between 680 and 700 and you're trying to decide, the relevant question isn't "which is cheaper per month" -- it's whether raising your score 20 points in the next 60 days is realistic. Lowering your credit utilization below 30% alone can add 20-40 points in a single billing cycle. If you can do that, conventional PMI becomes the clear winner. A buyer weighing this choice should also look at exactly what it takes to move a score 40-60 points before closing.

The tax angle most buyers miss

Here's the wrinkle that changes the math for higher earners: PMI isn't tax-deductible. The PMI deduction (Section 163(h)(3) of the tax code) expired after 2021 and has not been renewed by Congress as of 2026. You pay that $142 or $194 or $257 per month with after-tax dollars.

Mortgage interest, by contrast, is deductible on up to $750,000 in combined loan debt. In the piggyback structure, both the first and second mortgage are mortgage debt -- so the interest on that 8.5% second loan is deductible. For a buyer in the 24% federal bracket (single filer with income over roughly $103k in 2026), the second mortgage generates roughly $2,975 in interest in year one. The deduction is worth about $714 annually, or $60/month in tax savings.

That $60/month shifts the comparison modestly in favor of the piggyback for high earners. At 720+ credit, the conventional PMI route still wins ($2,127 minus no deduction vs $2,198 minus $60 = $2,138 after-tax). The gap narrows but doesn't flip at this credit tier. At 700-719 credit, it gets very close.

The important caveat: the standard deduction is $15,000 for single filers and $30,000 for married filers in 2026. You only benefit from itemizing if your total itemized deductions exceed those thresholds. Many buyers in the 22-24% bracket don't itemize -- which means the mortgage interest deduction advantage of the piggyback is zero for them. Don't assume it applies until you run your actual tax situation.

The long-term picture reverses

Month-to-month analysis is only part of the picture. The piggyback structure has a long-term advantage that conventional PMI can't match: the second mortgage pays off completely in 10 years. After that, you're carrying only the $280,000 first mortgage at 6.47%, with a P&I of $1,764/month.

With conventional PMI, you'll eventually cancel your PMI too -- but that requires reaching 80% LTV on the $315,000 first mortgage, which takes roughly 96 months (8 years) at the current amortization rate. After PMI cancels, you're still paying P&I on the full $315,000 first mortgage: $1,985/month.

So once both "extras" are gone, the piggyback structure costs $221/month less per month indefinitely ($1,985 vs $1,764). For a buyer with 720+ credit who paid an extra $71/month for 8 years with the conventional structure before PMI cancellation -- and then an extra $213/month for the two years after PMI cancelled but before the second mortgage finished -- the total extra cost is about $8,208. At $221/month savings starting month 121, the payback takes about 37 months. Long-term break-even: roughly 13 years from purchase.

If you're buying a home you expect to stay in for 15+ years, the piggyback probably wins even at 720+ credit. If you're planning to sell or refinance within 8 years, take the conventional PMI. Most buyers in their mid-30s buying a starter home aren't staying 15 years -- they're moving up in 7 to 9.

One more consideration: the second mortgage rate isn't fixed forever

Some lenders offer the 10% second as a fixed-rate closed loan (what's been modeled here at 8.5%). Others offer it as a HELOC -- a variable-rate line of credit currently tied to prime rate. Prime is 6.50-6.75% as of June 2026. A HELOC at prime + 1.5% runs about 8.0-8.25% today, slightly lower than a fixed second. But prime moves with the Fed funds rate. If the Fed hikes in December 2026 as CME FedWatch now prices at 68% probability, that HELOC rate goes up, not down. Locking in a fixed-rate second at 8.5% has an advantage in a rising-rate environment. If you use a HELOC for the second position, stress-test your payment at 10%.

Also worth knowing: PMI must be canceled by your lender at 80% LTV -- it isn't automatic. You have to request it. Plenty of borrowers continue paying it for years past the cancellation date. If you choose conventional PMI, set a calendar reminder for 7.5 years out to request cancellation, and call your servicer when you think your home's value has risen enough to get there early.

The rate shopping variable

The analysis above assumes you get the same 6.47% rate whether you go conventional or piggyback. That may not be true. The piggyback first mortgage is at 80% LTV, which faces lower Loan Level Price Adjustments from Fannie Mae than a 90% LTV loan. Depending on your credit score, the first mortgage in a piggyback structure might actually carry a slightly lower rate than a single 90% LTV loan -- widening the advantage of the piggyback a little further.

The gap on this tends to run 0.0% to 0.15% depending on credit tier. It's real but small. It won't flip the math at 720+ credit, but it may tip a 700-719 situation toward the piggyback. Get rate quotes for both structures from at least two lenders before deciding -- a mortgage broker who shops wholesale rates can often get you better numbers on the second than going direct to a bank. And be sure you're comparing total monthly cost including PMI, not just the rate itself. Lenders who quote you a lower rate on the conventional while omitting or low-balling the PMI estimate are not giving you a fair comparison.

The call

The math points toward this: if your credit score is 700 or above and you're buying a home you plan to own for fewer than 12 years, take the conventional loan with PMI. It's cheaper every month, you have a legal right to cancel it at 80% LTV, and you avoid the complexity of a second mortgage. If your credit is below 680, the piggyback wins from day one by $44 to $220/month depending on your score tier. If you're between 680 and 700, the piggyback is a small winner month-to-month -- but spend 60 days trying to raise your score first. A 20-point move at this tier eliminates the PMI advantage entirely and saves you the higher-rate second loan as well. Also see our breakdown of what closing costs come with each structure -- the piggyback adds a second set of origination costs that can run $500-$1,200 and should factor into your break-even.

Frankly, most buyers in the 680-720 credit range who are asking this question should be asking a different one: "What's the fastest way to get my score above 720?" The answer changes the entire calculus.