City code says three unrelated adults. My house has four bedrooms.

Before you write off the fourth room, check whether the code says three unrelated persons or three unrelated persons plus a resident owner. Some ordinances carve out owner-occupied, and some university towns have a separate rooming house license that permits more with an annual inspection. It's worth an actual call to the planning department, not a reading of the PDF.

Enforcement in the college towns I've looked at is almost always complaint-driven. Neighbor calls about cars on the lawn, inspector shows up. Nobody audits.

The shared study version might be worth more than 0. Three rooms at 750 with a real desk space in a fourth room beats three rooms at 700 in a house with an empty room, and that's 150 a month for the cost of some furniture. Doesn't close your gap but it narrows it.

If you ever want to borrow against it, a lender is going to underwrite the legal use. A four-room rent roll in a three-unrelated zone is an appraisal and underwriting problem later, even if nobody enforces it now.

Special use permits and rooming house licenses are real in some cities and effectively unobtainable in others, and the difference is usually political rather than procedural. The mechanism to look for is in the zoning code itself: search the text for rooming house, boarding house, lodging house, and dwelling unit occupancy. If the code creates that use category and lists the zones where it's permitted or permitted by special exception, there's a path. If R-1 isn't among the listed zones, a special use permit won't get you there and you'd be looking at a rezoning or a variance, which is a much heavier lift and usually requires showing hardship. How the family definition and any exception applies to your specific parcel is a question for a local land use attorney, and one hour of that will be cheaper than guessing.

On enforcement, most municipalities enforce occupancy limits on complaint, typically from a neighbor, and the consequences are usually a notice to abate with a deadline, then daily fines. The larger exposure is on the other side of the file. An unpermitted use can show up as a title or insurance problem on sale, a carrier can deny a claim if the occupancy on the policy doesn't match the actual use, and a lender who discovers it during a refinance can decline.

Your math is the part worth revisiting. Three rooms at 700 against a 1,900 whole house lease, with you paying 370 of utilities and internet, puts the by-room version at 1,730 net of those items before cleaning and per-room turnover. That's below the whole house number. The assumption to test is the 700. If rooms eleven blocks from a 22,000 student campus sign at 800 to 850, the three-room version works. Call five current listings and find out what they're actually signing at before you decide.

The rent number is doing everything here. I've been trying to figure out which strategy fits me and this thread is a good example of why I keep stalling: the whole decision turns on one comp you haven't verified yet.

Eleven blocks is also further from campus than it sounds to a sophomore without a car. Find out where the bus line runs, because in the college towns I've looked at, the room rents drop off a cliff past whatever the walkable radius is and then flatten out along transit.

Question I'd want answered before any of the rest: is a 4 bed 1.5 bath even a three-room co-living house? Three unrelated adults sharing one full bath plus a half is going to be a complaint in month two, and it caps who applies. That might be more of a constraint on your 700 than the ordinance is.