The listing says “great investment, fully rented.” The seller’s rent roll looks clean. Your agent says it’ll go fast.
Slow down.
Most duplex disasters aren’t about the building. They’re about what the buyer didn’t verify: the leases, the tenants, the deposits, the shared systems, the zoning. Here’s how to buy a duplex the way I’d buy one, in order.
Step one: decide if it fits your buy box
Before you look at a single photo, know what you’re buying and why. My rental buy box focuses on small multifamily within about an hour’s drive of the Midlands. Your box might be different. But you need one, or every listing will look like a maybe.
If you plan to live in one side, read house hacking first. The financing, the analysis and the lifestyle are different from a pure investment purchase.
Step two: analyze unit by unit
A duplex investment is two income streams. Analyze them separately.
Rent each unit on its own comps. One side might have more bedrooms, a better layout, a yard or a washer hookup. Don’t assume they rent the same.
Run the 1% rule screen against all-in cost: purchase plus repairs plus closing. Monthly rent across both units needs to be at least 1% of that. If it fails, I’m out. Explained on the 1 percent rule page.
Build the full operating budget. Vacancy, repairs, capex, management, taxes, insurance, and every owner-paid utility. On a duplex, find out who pays water, sewer and trash. It’s often the owner.
Check the purchase price against roughly the 70% rule: after-repair value times the rule, minus repairs. For duplexes, ARV usually comes from sold comps of similar 2-unit properties nearby, so pull real comps. The comps guide shows how I do it.
The formulas themselves, NOI, cap rate, cash-on-cash, are in my rental underwriting walkthrough.
Step three: confirm legal use
This one gets skipped a lot. Some “duplexes” are single family houses that someone split without permits.
- Confirm with the local zoning or planning office that two units are a permitted use.
- Check whether permits exist for the conversion, if it was converted.
- Look at the tax record’s classification.
- Ask whether each unit has its own address and meter.
If the second unit isn’t legal, your second rent check may not be either. And a lender or appraiser may value it as a single family home.
Step four: inspect every unit
Not “the good one and a peek at the other.” Every unit, every system.
Shared systems deserve extra attention: roof, foundation, sewer line, main electrical service, any shared water heater or boiler. One failure there hits both tenants at once.
Per-unit systems: HVAC, water heater, panel, plumbing fixtures, appliances, windows, flooring. Note the age and condition of each. That’s your capex forecast.
Life safety: smoke and carbon monoxide detectors, egress, fire separation between units where required.
Walk it with a repair sheet. Get a professional inspection. If something worries you, bring in the specialist. Learn the deal-killers on red flags when buying investment property.
Step five: tenants in place, leases and estoppels
Buying an occupied duplex means buying the seller’s decisions. Verify all of them.
Read every lease
- Names on the lease, rent, term, renewal terms.
- Deposit amount and where it’s held.
- Who pays which utilities.
- Pet terms, parking, any special promises.
Compare leases to the rent roll
They should match. If the rent roll shows something different from the lease, ask why, in writing.
Get tenant estoppel certificates
An estoppel is a signed statement from each tenant confirming their rent, deposit, lease term, what’s been paid, and whether there are side deals or disputes. It protects you from discovering after closing that “the seller said I don’t have to pay in December.” Have your closing attorney prepare or review the form and make delivery a condition in your contract.
Confirm deposits and prepaid rent
Deposits and prepaid rent are generally handled at closing. Make sure your attorney accounts for them.
Ask about payment history
Ask for whatever ledger or proof the seller will provide. A tenant who’s been chronically late is a tenant you’re about to inherit.
Step six: duplex financing
Duplexes are generally financed as residential property, which keeps the loan options broad. If you live in one unit, owner-occupant programs may apply. If not, investor options include conventional investment loans and DSCR loans, among others. Each has its own rules about reserves, how rental income is counted and occupancy. I cover one common investor option on the DSCR loans page.
I’m not a lender. Talk to one before you make an offer, and get requirements in writing.
Step seven: close with an attorney
In South Carolina, real estate closings are attorney-supervised. Pick a closing attorney with investor experience who understands tenant-occupied transfers, deposits and estoppels. More on that on the SC closing attorneys page.
After closing, send tenants a written notice about the new ownership and where to pay rent. Then do your own walk-through and start your own records from day one.
Your next step
Got a duplex under consideration? Post it in REI Skool, my free community, with both units’ rents, the leases’ key terms and your repair list. Let experienced investors poke at it before you sign. For the bigger picture on why I like two-to-four unit buildings, go back to the small multifamily investing home page.
Questions people ask
What is a tenant estoppel certificate?
It’s a signed statement from a tenant confirming the key facts of their lease: rent, deposit, term, what’s paid, and any side agreements or disputes. Buyers use it to confirm the seller’s rent roll matches what the tenant believes. Have your attorney prepare or review the form.
How do you finance a duplex?
Duplexes are generally financed as residential property. If you’ll live in one unit, owner-occupant programs may apply; if not, investor loans such as conventional investment loans or DSCR loans are common. Each program has its own rules, so talk to a lender before you make an offer.
Should I buy a duplex with tenants already in place?
It can be a good thing, since it means income from day one. It can also mean inheriting below-market leases, problem tenants or missing deposits. Read every lease, get estoppels, inspect every unit and confirm the deposits before closing.