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Author: Mark Ainely | Partner GC Realty & Development & Co-Host Straight Up Chicago Investor Podcast
As the co-host of Straight Up Chicago Investor and as a partner at GC Realty where we manage roughly 1,500 units across Chicagoland, I get asked the same question almost every week. Should I buy a 2 unit, a 3 unit, or a 4 unit?
Almost every new investor asking that question is after the same thing. They want to house hack. Live in one unit, rent the others, let the tenants pay down the mortgage while they build equity, and then either refinance, sell, or repeat the process on the next building. It is one of the best on ramps into Chicago real estate, and I still tell people it is the single fastest way to go from W2 employee to real investor in this city.
But here is what gets overlooked. A 3 unit is not just a 2 unit with one extra door, and it is not a smaller version of a 4 unit. Buying a 3 flat in Chicago comes with its own set of zoning considerations, ordinance exposure, and rentability questions that you do not face the same way on a 2 unit or a 4 unit. The listing agent is not going to walk you through any of it. That is my job today.
If you are circling a 3 flat right now, I want you to understand the two things that make a 3 unit different from a 2 unit or a 4 unit. Thinking you bought a legal 3 unit when you actually bought a 2 flat with a non conforming third unit. And getting blindsided by the FHA Self Sufficiency Test at underwriting and losing your financing days before closing. Neither of these show up on a 2 unit. One of them is easier to pass on a 4 unit. Both of them hit 3 unit buyers uniquely.
Let me break it down.
3 Flat Trap #1: Is It Really a Legal 3 Unit, or a 2 Flat With a Third Unit That Might Not Be Legal?
This is the single biggest mistake I see first time 3 flat buyers make in Chicago. A property gets marketed as a 3 unit. You walk through three doors, three kitchens, and there is a tenant paying rent in each space. You assume you are buying a legal 3 unit.
You are not always.
There is a massive difference between a building with three legal units above grade and a 2 flat with a non conforming basement or attic unit. In listing photos they can look identical. In reality they price differently, finance differently, and carry very different risk.
A true legal 3 unit was built as a 3 flat, or legally converted to three units, with permits, proper egress, code ceiling heights, and recognized unit separation. The city has the building on record as a 3 unit. Every unit is above grade, every unit conforms.
A 2 flat with a non conforming unit is a 2 flat where someone, somewhere along the way, added a kitchen and bathroom to the basement or attic and started renting it. The space may have a tenant in it paying rent today. It may be perfectly livable in practice. But the city does not recognize it as a legal dwelling unit, and that changes everything about the deal.
Here is why this matters:
Pricing. A true legal 3 unit trades at a premium to a 2 flat with a non conforming unit. Sellers and listing agents still price these buildings off legal 3 flat comps because that is what they want you to pay. If you do not catch it, you overpay.
Your lender may not count the third unit in the appraisal. This is the one that kills house hackers. When the appraiser pulls city records, if Chicago has the property recorded as a 2 flat, the appraisal is going to come in as a 2 flat. The rent from the non conforming unit does not get credited into your income, your loan to value, or your debt coverage. Your financing gets rebuilt off a smaller number, and the deal that penciled at a legal 3 unit price stops penciling.
Legalization is long, expensive, and not guaranteed. Investors tell themselves they will just legalize the third unit after closing. In practice this is a 6 to 12 month process that can run $50,000 to $150,000 or more depending on what the city requires. You may need egress window wells, a second means of egress, raised basement ceiling heights, fire rated separation between units, updated mechanicals, separate metering, and architectural drawings signed off through the Department of Buildings. That is all assuming the zoning even allows three legal units on your lot, and this is where the R2, R3, R4, R5 labels actually matter. On a standard 25 by 125 Chicago lot (3,125 square feet), R2 allows one unit per 5,000 square feet and R3 allows one unit per 2,500 square feet. Both are effectively single family on a standard lot, so you cannot legalize a third unit there regardless of what you spend. R4 allows one unit per 1,000 square feet, which means three units by right, and this is where legalization is realistic. R5 opens up even more density. That non conforming basement unit is rentable today because the prior owner flew under the radar. Whether it is legalizable tomorrow depends almost entirely on what that zoning label says.
How to verify before you write an offer. Pull city records. Check the Department of Buildings permit history on the address. Check the Cook County Assessor for the recorded unit count. Look at the zoning label. Ask the listing agent for a certificate of occupancy showing three legal units. If the seller cannot produce documentation that the city recognizes this building as a 3 unit, you are almost certainly looking at a 2 flat with a non conforming third unit.
None of this is automatically a deal killer. But it is a different deal than what is being advertised. Price it like a 2 flat, finance it like a 2 flat, and treat the income from the non conforming unit as upside, not base case. Budget the time and money to either legalize it or to operate it with eyes wide open.
This is also where the 2 versus 3 versus 4 unit question gets real. On a 2 flat, basement or attic income is cosmetic upside, not the business case, and the deal still works without it. On a 4 flat, financing is still residential and owner occupied house hacking still qualifies, but you need R5 density or a larger lot to get there conforming. The 3 flat sits right on the pivot point. It is the exact size where an informed buyer can identify a mispriced 2 flat on an R4 lot with a real path to legalizing a third unit and turn it into a cash flow machine. It is also the exact size where an uninformed buyer overpays for paper income that the lender (and eventually the city) do not back up.
3 Flat Trap #2: The FHA Self Sufficiency Test That Hits 3 Unit Buyers the Hardest
If you are planning to house hack with FHA financing, and most first time 3 flat buyers are, you need to understand a specific lending test that Chris Puleo of The Puleo Group walked us through on Straight Up Chicago Investor. It is called the FHA Self Sufficiency Test, and it is the single biggest reason a 3 unit deal can fall apart at underwriting while a nearly identical 2 unit or 4 unit deal sails through.
Here is how it works, straight from Chris on the show:
On 1 and 2 unit properties, the Self Sufficiency Test does not apply.
On 3 and 4 unit properties, the test does apply.
You take all unit market rents, or current rents, whichever is lower. You multiply by 75 percent. That number is the maximum mortgage payment (PITI) the property can carry.
If your projected PITI is higher than 75 percent of gross rents, FHA will not approve at 3.5 percent down. You have to put more money down until the math clears. In Chicago, where property taxes and insurance are brutally high in certain pockets, that can be a huge number.
Here is why this matters specifically for the 2 versus 3 versus 4 unit question, and why the 3 unit gets squeezed the hardest:
2 unit: No test. You are evaluated on your personal income and debt ratios. You can qualify with 3.5 percent down on FHA with no property level performance test to pass.
4 unit: Test applies, but you have four rent streams at 75 percent to cover PITI. In most Chicago neighborhoods, the math clears on market rents.
3 unit: Test applies, and you only have three rent streams at 75 percent to cover PITI. In high tax pockets (most of the north and northwest sides, plus parts of the west side), this is where house hackers get surprised at the closing table and have to scramble for more down payment. Or they lose the deal.
The 3 unit is the worst of both worlds for an FHA house hacker. You get the test AND you get fewer units of rent to pass it with.
Here is what I tell every investor shopping for their first 3 flat:
Run the test before you write an offer, not after. Send the listing (with projected market rents, pulled from real signed comps, not pro forma) to your FHA lender and have them back out the numbers. If the deal fails the test at 3.5 percent down, you either need more cash, a different loan product, or a different building. You want to know that in writing before you sign the contract.
Compare FHA to the 5 percent down conventional option. Chris and Tom covered this update on the show too. Fannie Mae dropped the down payment requirement on 2 to 4 unit owner occupied properties to as little as 5 percent. That is a massive shift from the old 15 percent down on 2 units and 25 percent down on 3 and 4 units. The conventional product does not use the FHA Self Sufficiency Test, so on some 3 unit deals the 5 percent down conventional loan is actually cheaper out of pocket than the 3.5 percent FHA loan once you factor in what you need to put down to pass the test. Run both numbers side by side.
Underwrite to the lower of market or current rent. The FHA test uses whichever is lower. If your target building has units leased to long term tenants at below market rents, you are going to be tested against those lower numbers. That is where people get burned. Ask the listing agent for current rent rolls early.
The practitioner takeaway: if you are committed to FHA house hacking, run the Self Sufficiency Test math early in every deal. If the 3 unit you love does not pencil at 3.5 percent down, a 4 unit may actually be an easier FHA path, a 2 unit avoids the test entirely, and 5 percent conventional may be the cleanest alternative of all. This is not the kind of thing you discover three days before closing.
The Questions to Ask Before You Sign
I keep this list in my head every time I walk a 3 flat. You should too:
Can the seller produce a certificate of occupancy showing three legal units, and does the Department of Buildings and the Cook County Assessor both confirm the unit count?
What is the exact zoning label on this lot, and does it allow three legal units, or is the current unit count grandfathered or non conforming?
If the basement or attic is being used as a unit, is it legal, separately metered, and egress compliant, and what will it cost to legalize if not?
Has my FHA lender run the Self Sufficiency Test on this deal using the lower of market rents or current rents, and does it pass at 3.5 percent down?
If the FHA test does not pencil, have I compared it to a 5 percent down conventional loan before walking away?
If you cannot answer those five questions with confidence before the inspection period ends, you are not ready to close.
Don't Go At This Alone
The Chicago 3 flat is still one of the most accessible ways into this business. I have bought them, renovated them, managed them, and sold them for 20+ years. But the 3 unit specifically comes with a legal unit count question and a lender underwriting test that a 2 unit or a 4 unit does not put you through the same way. Miss either one and a deal that looked great on paper can blow up at the closing table.
If you are looking at a 3 flat right now and you want a second set of eyes before you write, reach out. We help investors across the city and suburbs think through these exact decisions every week, whether that is through our tenant placement and property management services, or just an honest gut check call on a deal.
Best Investing,
