Cross an invisible line — from four units to five — and everything you know about mortgages stops applying. Different math, different documents, different risks, even a different definition of what the building is worth. That line has a history, and on the commercial side of it, the property itself becomes the borrower. Here's how that world actually works.
Why the Line Sits at Four Units
When Congress chartered Fannie Mae and wrote the FHA's rules, it drew the boundary of "residential" at properties a family might plausibly live in: one to four units. Five and up was deemed a business — and businesses were left to the banks. That charter decision, made generations ago, is why a fourplex finances like a house and a five-unit building finances like a factory. Commercial real estate lending itself is as old as banking, but its modern form arrived in the 1990s: after the savings-and-loan collapse, the government's Resolution Trust Corporation packaged seized commercial mortgages into bonds to sell them off — accidentally inventing the CMBS market that, alongside banks and credit unions, funds much of commercial property today.
The Big Mental Shift: Value Is Manufactured, Not Found
A house is worth what similar houses sold for. A commercial building is worth its income: value = net operating income ÷ cap rate. That formula changes everything, because it means value can be engineered. Raise rents $200 across ten units and you've added $24,000 of NOI; at a 7% cap rate, you just created roughly $340,000 of value — no comparable sales required. This is the entire game of commercial real estate: buy underperforming income, fix the income, harvest the value. Lenders underwrite that same logic.
How Commercial Loans Are Built
- DSCR rules the file: lenders want the property's income covering the payment by 1.20–1.25× — the same ratio logic from investor lending, at bigger scale
- Down payments of 20–30%, sometimes more for specialty property types
- Shorter commitments: the 30-year fixed doesn't exist here. Typical structure: a rate fixed for 5, 7, or 10 years, amortized over 20–25, with a balloon — the balance due, expected to be refinanced or the property sold
- Recourse matters: many loans require personal guarantees; larger deals can be non-recourse (with "bad-boy" carve-outs). This clause deserves more negotiation than the rate does
- The document stack: rent rolls, operating statements, sometimes environmental reports — the building gets audited like the small business it is
The Analysis: Balloons Are the Real Risk
Here's the honest lecture most commercial borrowers get too late: the danger in commercial debt usually isn't the rate — it's the maturity. That balloon lands on a schedule that doesn't care what the market looks like when it arrives. The office-building carnage of 2023–24 was exactly this mechanism: loans written at 3.5% maturing into a 7% world with lower occupancy, with no choice but to refinance at brutal terms or hand back keys. The defense is structural, decided on day one: match the fixed period to your business plan, model the refi at stress-test rates (not today's), and treat the amortization schedule as your equity-building engine between now and the balloon. A commercial loan isn't a product you pick; it's a five-to-ten-year plan you architect.
When Commercial Financing Is the Wrong Move
- Mixed-use with a small commercial footprint — some 1–4 unit properties with a storefront can still finance residentially, which is almost always cheaper
- You're at 4 units and stretching to 5 "to scale" — that fifth unit swaps you into commercial underwriting, pricing, and balloons; sometimes two fourplexes beat one eight-unit
- Thin operating history — commercial lenders underwrite the income; a building with no stabilized rent roll needs a bridge plan, not a permanent loan
The Bottom Line
Commercial lending judges the building's business, not your paycheck — which means the deal is won or lost in how the file tells the property's income story. That's a craft. Bring me the rent roll and the plan; I'll tell you how a lender will read it before a lender ever does.
Have a Deal in Mind?
Rent roll, price, and your plan — I'll model the DSCR, the balloon, and the structure a lender will actually say yes to.
Talk It Through →Questions? Call or text (224) 591-3179 or write to benmortgages2008@gmail.com.