3% Assumable FHA vs. 6.5% Conventional
A property has an assumable FHA loan at 3%. But closing the gap costs $92K cash. A conventional at 6.5% needs less upfront. Which path wins over 10 years?
You find a 3-bedroom SFR listed at $340,000 in a B neighborhood — solid rental demand, stable schools, low vacancy. The property cash flows on day one with either financing path. But the seller has something most listings don't: an assumable FHA mortgage from 2021.
Here's what you're working with:
- Assumable FHA balance: $248,000 at 3.0% fixed (25 years remaining)
- Gap to close: $92,000 cash (no second mortgage allowed on FHA assumptions)
- Conventional alternative: 25% down ($85,000), 6.5% fixed, 30-year term
- Monthly rent: $2,450
- Your available cash: $105,000
Two paths to the same property. Very different math.
You run the 10-year interest comparison and the assumable mortgage looks like a different asset class entirely:
- Assumable payment (P&I): $1,176/month
- Conventional payment (P&I): $1,612/month
- Monthly savings: $436
- 10-year interest saved: $91,170 ($154,590 conventional vs. $63,420 assumable) — plus $38,880 more in principal paid down
But here's the catch: after the $92K assumption gap, you're left with $13,000 in reserves. One busted HVAC system and a vacancy at the same time, and you're liquidating something to stay solvent. The conventional path leaves you with $20,000 in reserves — almost double.
Assume the FHA loan and keep $13K in reserves. The $130,000 in 10-year savings is generational wealth-building. You can rebuild reserves from the $436/month cash flow difference within two years.
Go conventional at 6.5% and keep $20K in reserves. Liquidity beats rate every time. A 3% rate means nothing if one bad quarter forces you to sell the property at a loss.
Assume the loan and negotiate seller financing for the $7K gap. Ask the seller to carry a $7K note at 5% for 24 months. You keep $20K in reserves AND get the 3% rate on $248K of the debt.
The Rate Is a Gift. The Cash Requirement Is the Price.
Option A is the right instinct. Option C is the right execution.
Let's be honest about what a 3% fixed rate means in a 6.5% world: it's a $130,000 head start over 10 years. That's not a rounding error. That's not a marginal improvement. That's the difference between a property that builds wealth and a property that treads water. Every month, $436 stays in your pocket instead of going to a lender. Over a decade, that buys you another down payment on a second property — funded entirely by the rate spread.
So why wouldn't you just grab Option A and move on?
Because $13,000 in reserves on a rental property is playing with fire. I've watched investors lose properties not because the deal was bad, but because the deal was tight. A $6,800 HVAC replacement in July. A tenant who stops paying in August. An insurance premium that jumps $1,200 at renewal. None of those are unlikely — they're inevitable on a long enough timeline. And when they stack on each other, $13K evaporates in a single quarter.
That's why Option B exists. The conventional path is boring, and boring keeps you solvent. You lose $436/month in rate savings, sure. But you gain breathing room. You gain the ability to survive a bad quarter without calling your mortgage servicer from a position of desperation.
But Option C is where discipline meets opportunity. Here's what most investors don't realize about assumable mortgages: the gap between the loan balance and the purchase price doesn't have to be all cash. The $7,000 difference between the $92K gap and the $85K conventional down payment is a small enough number that many sellers will carry it as a short-term note. A $7,000 seller-carry note at 5% over 24 months costs you roughly $307/month for two years — and then it's gone. Meanwhile, you're paying 3% on $248,000 of the debt instead of 6.5% on $255,000.
The math on Option C:
- Cash at closing: $85,000 (same as conventional)
- Reserves remaining: $20,000 (same as conventional)
- Monthly P&I on assumed loan: $1,176
- Monthly seller note payment: $307 (for 24 months only)
- Year 1-2 total payment: $1,483/month (vs. $1,612 conventional)
- Year 3+ payment: $1,176/month (vs. $1,612 conventional — saving $436/month)
You get the generational rate. You keep conventional-level reserves. And after 24 months, your payment drops by $436/month compared to where it would have been. The seller gets their full $340,000 — they have no reason to say no to a $7K note when the alternative is losing the deal entirely.
The real lesson here isn't about FHA assumptions. It's about structuring the capital stack so the deal works at every layer — rate, reserves, and risk tolerance. A 3% rate with $13K in reserves is a fragile deal. A 3% rate with $20K in reserves and a 24-month seller note is an engineered outcome. Same property. Same rate. Completely different risk profile.
Never let a great rate convince you to accept a thin margin. Structure the gap, protect your reserves, and let the rate do its work over time.
- An assumable mortgage at 3% vs. 6.5% conventional saves roughly $436/month — that compounds into six figures over a decade
- The gap between the assumable balance and the purchase price is the real cost of assumption — not just the down payment, the TOTAL cash requirement
- Reserves under $15K on a single-family rental are a red zone — one compounding event (vacancy + repair) can force a distressed sale
- Seller financing on a small gap amount ($5K-$15K) is negotiable — the seller still gets their full price
- The best financing decision accounts for the next 3 deals, not just this one
