Does the residential loan edge survive going from three fourplexes to one twelve-unit?

The piece I'd add on the twelve-unit side is that at that size you can support a part-time onsite person or at least one management company relationship with real attention. Three fourplexes at three addresses with $1,200 rents is the account size that gets handed to whoever is newest at the PM company. That's not a financing cost but it lands in the same place.

Drive time is the underrated line. Turnover work, showings, contractor meets, three addresses spread across town means every vendor charges you a trip charge three times instead of once. On a twelve-unit I can get a painter to bid two turns in a week. Ask the shops you'd hire what they'd quote for a scattered four-door account versus one twelve, because sometimes the percentage is identical and the service isn't.

On your last question: agency guidelines have historically capped the number of financed properties a single borrower can hold, and past that you're into portfolio and DSCR lenders whose terms look more like the commercial quote you already have. So the residential edge isn't infinite, it's a runway. Confirm the current count and how they define a financed property with your lender in writing, because partnerships and entity-held loans get counted in ways people don't expect. The balloon is the item I'd price hardest. Five-year money on a twelve-unit means you're refinancing into an unknown rate environment with an appraisal that depends on that building's NOI at that moment. A 30-year fixed on a fourplex has no such date on the calendar.

I'm at the point where scattered small buildings are what's slowing me down, and the cost isn't the interest rate. It's that every property has its own tax appeal deadline, its own insurance renewal, its own water utility with its own account portal. Four doors of income with one building's worth of admin is the fourplex pitch, and it holds until you own several of them and discover the admin was per building all along. Whether that beats a balloon I genuinely don't know. Tender's point about the refinance date is the one that would keep me on the residential side.