A duplex puts two rents under one roof, so for the same price it can bring in more than a house. It also asks for a bigger down payment, can come with bills the owner pays, and has two tenants who can each move out. Below, the same $375,000 buys each one, and every difference gets a number.
Does a duplex make more money than a house at the same price?
A duplex makes more only when its two rents beat the house’s rent by enough to pay for what it adds.
Both properties cost $375,000 on a 30-year loan at 7%, with $350 a month of property taxes and $150 of insurance. Both set aside 5% of rent for empty months and 18% for repairs, big repairs and a property manager. The house rents for $3,300, and its tenant pays all the utilities. The duplex has two units at $1,800 and one water meter, so its owner pays $120 a month for water, sewer and trash. The house is bought with 20% down and the duplex with 25%, for a reason the next section explains. The last column is the duplex in a month when one unit has no tenant.
| House | Duplex | Duplex, one unit empty | |
|---|---|---|---|
| Rent | $3,300 | $3,600 | $1,800 |
| Empty months (5% of rent) | −$165 | −$180 | – |
| Property taxes and insurance | −$500 | −$500 | −$500 |
| Water, sewer and trash | – | −$120 | −$120 |
| Repairs, big repairs and management (18% of rent) | −$594 | −$648 | −$324 |
| Mortgage | −$1,996 | −$1,871 | −$1,871 |
| Cash flow each month | +$45 | +$281 | −$1,015 |
These are example figures, not a forecast for any market.
With both units let, the duplex keeps $281 a month and the house $45. Neither has much to spare, and the calculators give both the same verdict: “Cutting it close.” The duplex’s $236 lead looks like the second rent at work. Less than half of it is.
How much more cash does a duplex need than a house?
If you won’t live in either one, a standard loan (one without government backing) asks for a bigger down payment on the duplex. As of September 2026, Freddie Mac’s limits for the loans it buys cap the loan at 85% of the price on a one-unit rental and 75% on a rental with two to four units. That means at least 15% down on the house and 25% on the duplex. A lender can ask for more.
| House, 15% down | House, 20% down | Duplex, 25% down | |
|---|---|---|---|
| Down payment | $56,250 | $75,000 | $93,750 |
| Closing costs (3%) | $11,250 | $11,250 | $11,250 |
| Cash to buy | $67,500 | $86,250 | $105,000 |
At the smallest down payments those limits allow, the duplex takes $37,500 more cash. The house’s smaller check has a cost, though. Under 20% down, a standard loan can require private mortgage insurance, which protects the lender, not you. And at 15% down, the bigger loan alone would turn the house’s $45 into an $80 monthly loss. So this example buys the house with 20% down, and the duplex takes $18,750 more.
That $18,750 buys a smaller loan, $281,250 instead of $300,000, with a payment $125 a month lower. Give the house the same 25% down and it keeps $170 a month. Of the duplex’s $236 lead, then, $125 comes from the extra cash and $111 from the building: $300 more rent, less the 23% of it set aside for empty months, repairs and management, less the $120 water bill.
The cash-on-cash return, a year’s cash flow divided by the cash you put in, is 3.2% on the duplex’s $105,000 and 0.6% on the house’s $86,250. Put the same cash into both and the duplex stays ahead only while its units rent for more than about $1,728 each, $156 a month more in all than the house.
Living in one unit changes these limits, and whether house hacking is worth it covers that case.
What happens when one duplex unit is empty?
One empty unit takes half the duplex’s rent, where an empty house loses all of it.
Say Unit 2 is empty the day you buy. In the multifamily calculator’s rent roll, untick Unit 2 under “Rented today” and a note appears: “One unit is empty right now, which is 50% vacancy. The answer assumes 5%, so it describes the building once that unit is let.” The $281 describes the building with both units let. To see the month you’d actually have, set Unit 2’s rent and the vacancy rate to zero. That’s the first table’s last column: $1,015 out of your pocket each month until Unit 2 is let.
An empty house costs more. Its rent stops completely, and the month costs $2,496 in mortgage, taxes and insurance with nothing coming in. The catch is that the duplex has two leases, so two tenants can give notice, each taking half the rent.
Before you count on a rent for an empty unit, check it against what similar units rent for today, the way this duplex analysis does.
Do duplexes sit empty more often than houses?
The Census Bureau doesn’t publish a vacancy rate for duplexes alone, but its closest split finds more empty rentals in buildings with more than one unit.
In the second quarter of 2026, 8.4% of rentals in buildings with two or more units stood empty and for rent, against 5.7% in one-unit buildings, according to the Housing Vacancy Survey tables the Census Bureau released on July 28, 2026. The two-or-more group includes large apartment complexes, so treat the gap as a reason to ask local property managers how long units like these take to rent, not as a duplex’s own rate.
Plug those two rates in as the allowances for empty months instead of 5%, and the house keeps $22 a month and the duplex $158.
How do you compare a duplex and a house you’re looking at?
Run each property in its own calculator, with the same assumptions typed into both.
- Put the house in the rental calculator and the duplex in the multifamily calculator. The multifamily one opens on a fourplex, so step “Units in the building” down to 2 and enter each unit’s rent.
- Type the same price, interest rate, property tax, insurance and vacancy rate into both. Anything you leave alone comes from each calculator’s own example, and the two examples differ.
- Set the duplex’s Utilities to the bills its owner will pay, and its down payment to 25%. The multifamily calculator starts at 20%, and a standard loan on a two-to-four-unit rental you won’t live in needs at least 25%.
- Compare Monthly cash flow and Cash invested, then set one unit’s rent and the vacancy rate to zero to see the half-empty month the duplex would have to carry.