Is a duplex a good investment? The same $400,000 building, underwritten as a rental and as a house hack

“Is a duplex a good investment” is the wrong question by one word. A duplex is not one investment; it is two, and which one you get is decided by a single line on the loan application: do you live there?

The gap is not marginal. Conventional financing requires 25% down on a 2-4 unit investment purchase — there is no 15% or 20% tier the way there is for a single-family rental — while the same building owner-occupied takes 5% down conventional or 3.5% FHA, at primary-residence pricing: Fannie Mae's current matrix adds a 2.125%-of-loan price adjustment to a 75%-LTV investment purchase that an owner-occupied loan does not carry. Run one $400,000 duplex down both paths and the capital requirement is $138,140 against $58,129. Same roof, same tenants, same rents. About 2.4 times the money.

Every pros-and-cons article on this question lists “two income streams” and “you can use an FHA loan.” None of them prices the fork. This post does: the full underwrite of one duplex both ways, the year-2 problem that catches 5%-down buyers, and a head-to-head against a same-priced single-family where the duplex wins on yield and loses on exit.

Rate assumptions throughout: 7.25% on the investment loans and 6.75% on the owner-occupied ones, set in early August 2026, when the 30-year fixed on a primary residence ran roughly 6.65-6.875%. The 7.25% adds an assumed 0.50-point rate premium for an investment loan (Fannie Mae's actual investor charge is an upfront loan-level price adjustment, 2.125% of the loan at 70-75% LTV, so get a written quote). Freddie Mac's weekly survey average has since risen to 7.03% (September 24, 2026). PMI is modelled at 0.8% of the loan balance a year. Fees are typical, not quoted — your Loan Estimate is the only figure that binds.

The building we are underwriting

One duplex, priced and rented like real inventory in a balanced metro — the kind of two-unit stock that fills whole neighbourhoods in Philadelphia and Kansas City. Both paths below use identical property facts, so every difference in the results comes from the financing.

$3,200 on $400,000 is a 9.6% gross yield. Hold that number — it is the reason a duplex can survive a 25% down payment that would sink a single-family, and it is the first thing to check on any two-unit you are shown.

Path A: the duplex as a pure rental

Non-owner-occupied, 25% down, 7.25% on a 30-year fixed. The loan is $300,000 and principal and interest are $2,046.53 a month.

That produces a 5.31% cap rate, a DSCR of 0.86, and a cash-on-cash return of −2.7%. A 0.86 DSCR means NOI does not cover the payment; at this NOI, coverage only reaches 1.0 at about 35% down, and any lender minimum above 1.0 needs more. DSCR lenders define the ratio and minimum differently, so check the lender's formula. Check yours in the free TrueCap analyzer before you pay for an appraisal.

And the cash to get there:

$138,140 to lose $277 a month. That is not a broken example — it is what a 9.6%-gross-yield duplex does at a 7.25% investment rate with the minimum down payment, and it is why the honest answer to this question starts with the financing rather than the building. The reserve line is money you show rather than spend; the full five-bucket cash-to-close breakdown explains which is which.

Break-even, if you want it: NOI of $21,232 supports $1,769 a month of debt service, which at 7.25% is a loan of about $259,000 — 35% down, or $140,600. Ten points above the minimum.

Path B: the same duplex, owner-occupied

Now live in the left unit. The down payment drops to 5%, the rate prices at 6.75%, and the lender counts 75% of the appraiser's market rent on the other unit when qualifying you (with less than 12 months of property-management experience, it can offset the housing payment but not add to your income) — which is how a $400,000 purchase becomes reachable on a salary that would not carry it alone.

The loan is $380,000. P&I is $2,464.68, PMI at 0.8% is $253.33, taxes are $366.67 and insurance $200 — PITIA of $3,284.68.

Cash required: $20,000 down, $10,500 of closing costs, $4,921 of prepaids and escrow setup, $3,000 to make the rental unit ready — $38,421 spent — plus six months of reserves, $19,708, for $58,129 total. Living there does not shrink the reserve line: Fannie Mae requires six months of reserves on a two- to four-unit principal residence, measured in months of PITIA, the same as on an investment purchase. Size your own version in the analyzer in House Hack mode.

Is $1,988.68 good? Only against the alternative. The unit next door rents for $1,600, so living in your own duplex costs $389 a month more than renting the identical space — $4,668 a year. Against that, year-one principal paydown on the $380,000 loan is $4,050. The premium and the equity build cancel almost exactly, before any appreciation, and you now control a $400,000 asset for $20,000 down.

That is the honest version of “live for free.” You do not live for free. You live at roughly the cost of renting, with a leveraged asset attached and a landlord's job on top. Whether that trade is worth it is the subject of the house-hack underwriting guide; the occupancy rules and the one-year exit are in house hacking explained.

FHA at 3.5%, briefly

FHA (with a credit score of 580 or higher) takes the down payment to $14,000 and finances the 1.75% upfront premium into the loan ($6,755), giving a balance of $392,755 — P&I of $2,547.42 — plus annual MIP at 0.55% of $386,000, or $177 a month. PITIA lands at $3,291, within $7 of the 5%-down conventional payment. So FHA saves $6,000 of cash for essentially the same monthly cost, and charges for it later: above 90% LTV at origination the MIP never falls off, where conventional PMI on a Fannie Mae-backed two- to four-unit loan can be cancelled at your request once the balance reaches 70% of the original value, and otherwise ends automatically at the midpoint of the loan term. The 2026 FHA two-unit limit is $693,050 in low-cost areas (HUD's national floor), well above this example's $386,000 base loan.

The year-2 problem

Here is the part the pros-and-cons posts never reach. You live there for twelve months, which satisfies FHA's one-year occupancy intent and any one-year covenant in your conventional loan documents, you move out, you rent your unit. Both units now produce $1,600 and the property is a pure rental with an owner-occupied loan still attached.

Move to the same $2,400 landlord policy as Path A and add 8% management, and NOI is the Path A figure, $21,232. Debt service is $29,576 of P&I plus $3,040 of PMI — the balance is still 94% of value, nowhere near the 70% of original value at which Fannie Mae lets you cancel PMI on a two- to four-unit loan — for $32,616.

−$949 a month. The loan that made the purchase possible makes the rental unprofitable. And rent growth will not rescue it on any useful timeline: 3% on $38,400 is $1,152 of gross, which after the 27% of expenses that scale with rent and 3% growth on the $6,800 of fixed bills leaves about $637 of extra NOI in year three. Compounding that 3% forward against a fixed $32,616 of debt service, NOI grows into its own payment in roughly fifteen years.

So the 5%-down duplex needs an exit decided in advance. The real options are a refinance if rates fall (dropping to 6.0% on the $376,000 balance saves about $210 a month, and kills PMI only if the appraisal supports 75% LTV, Fannie Mae's refinance limit for a 2-4 unit investment property once you have moved out, or 80% LTV if you still live there), aggressive principal paydown, living there longer than a year, or selling into the residential buyer pool once you have owned and lived in your unit for at least two of the five years before the sale, when the home-sale exclusion can cover the gain on your own unit (not the rented unit or depreciation). What does not work is assuming the property becomes a good rental because you stopped living in it.

Duplex vs a same-priced single-family

The comparison most people actually want. Same $400,000, same metro, both as pure rentals. The single-family rents for $2,600 — a 7.8% gross yield against the duplex's 9.6%, which is the normal relationship, because a house sells partly on owner-occupant demand and a duplex mostly on rent. The single-family also gets the easier down payment: 20% conventional, or 15% if you accept mortgage insurance.

The duplex wins on every income measure, and the last row is the one that matters: it reaches break-even cash flow with $59,400 less capital than the same-priced house. The extra five points of down payment are the cheapest thing in the table — the $7,200 a year of extra gross rent repays the extra $20,000 of down payment in under three years. Both are in negative leverage at these rates; the duplex is simply less deep in it.

Run your own pair — the TrueCap analyzer takes about a minute per property and will hold both, so you can compare standardized economics rather than eyeball spreadsheets. For the wider property-type question, including where five-plus units change the rules, single-family vs multi-family goes further than this post does.

What a duplex structurally gives you

Shared fixed costs — about $1,800 a year

Two units under one roof on one parcel genuinely cost less to run than two houses. One landlord policy at $2,400 rather than two at $1,700 saves $1,000. One lawn and snow contract rather than two saves $600. One 1,600-square-foot roof at $12,000 rather than two 1,000-foot roofs at $9,000 each is about $240 a year amortised over 25 years. Turnover trips, inspections, and contractor minimums all collapse to one address.

Total: roughly $1,840, or 4.8% of gross rent — worth about half a point of cap rate. Note what is not on that list. Property taxes follow assessed value, so $400,000 of duplex is taxed like $400,000 of house; you do not save there, and that is where most people expect the saving to be. Water and sewer often go the wrong way, because many duplexes have a single meter and the landlord eats it.

Vacancy variance, halved

A single-family rental is 100% occupied or 0% occupied. A duplex has a middle state, and that middle state is the difference between an inconvenience and a crisis. When the single-family above goes empty you cover $2,183 of debt service out of pocket. When one duplex unit goes empty, the other unit's $1,600 covers 78% of the $2,047 payment and you are out $447.

The expected vacancy rate is the same — assume 6-8% either way — but the distribution is far kinder, and for a first or second property that softer downside is what keeps you solvent. Two units also means two lease-expiry dates you can deliberately stagger so you are never turning both at once.

One financing event, two doors

Two units acquired with one appraisal, one title policy, one origination fee, and one entry in your LTV and financed-property count. That last point compounds: Fannie Mae's reserve escalator and its ten-financed-property limit for second-home and investment loans count properties, not doors (a two-unit counts as one financed property), so a duplex reaches the same unit count as two houses while consuming half the slots.

What it structurally costs you

1. The 25% down payment. Already priced above — $20,000 more than a single-family at 20%, and no 15% escape hatch. On the owner-occupied path this reverses completely, which is the whole argument of this post.
2. A comps-based appraisal ceiling. Properties under five units are not valued by capitalizing NOI. Fannie Mae requires an income approach for 2-4 units, but it uses a gross rent multiplier drawn from comparable sales and cannot stand alone, so the appraisal still tracks what comparable duplexes sold for. Raise rents $100 a unit and a five-unit gains roughly $100,000 of appraised value at a 6% cap; a duplex gains far less. If your plan is to force value through operations, that plan needs five units.
3. A thinner exit. Your resale buyer pool is investors plus house hackers, not every family in the metro. Expect longer days on market and less competitive bidding, especially when rates are high and the investor pool is thin. This is real but hard to price; treat it as a reason to buy in a neighbourhood where duplexes are normal rather than the one odd two-unit on a street of houses.
4. Tenant proximity. Free to model and expensive to live. A shared wall means you hear every problem first, your tenant knows exactly where you live, and “I'll fix it this weekend” becomes a standing obligation. It is a real quality-of-life cost to weigh before you commit to a year of occupancy.
5. Doubled capex timing risk. Two kitchens, two baths, often two furnaces and two water heaters, and in older stock they tend to fail together because they were installed together. The 5% reserve above is a percentage of rent; check it against the actual component-by-component replacement schedule on any duplex built before 1990.

So: is a duplex a good investment?

Four decision rules, in the order they bind.

1. If you will live in it for a year, the owner-occupied path is where a duplex's structural edge sits. $58,129 of cash ($38,421 spent, the rest reserves you show the lender) for a $400,000 income-producing asset, at owner-occupied pricing without the investment-property price adjustment, on a loan that stays in place after you leave, is an advantage you get once per property. Price that path before the pure-rental one.
2. If you will not live in it, the gross yield has to clear 10%. At 9.6% our example loses $277 a month at the minimum down payment. Break-even needs 35% down. Below a 10% gross yield you are buying appreciation and a DSCR under 1.0 with capital you could have deployed at coverage above 1.2 in a cash-flow market.
3. Never model a 5%-down duplex as a rental without modelling the move-out. −$949 a month is the year-2 number on our example. Decide the refi, the paydown, or the sale before you sign.
4. Buy where duplexes are ordinary. The comps-based appraisal and the thin buyer pool are both survivable in a neighbourhood with a real two-unit comp set, and neither is survivable on a street of single-family houses.

More on the strategy fork — BRRRR, Section 8, house hacking, and how each one changes the same building — in the investing strategies guide. For the financing side, the down payment tiers and payment calculator will size the two paths against your own numbers in a couple of minutes.

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