Thinking about running turnovers as an actual business instead of just for my own units

Density is the one I'd stress-test first. Your margin math assumes ninety minutes of paid time per turn, but the drive between properties is also paid and it's unbillable. Ten units within four miles works. Ten units spread across a lake region and you're paying for a lot of driving at $110 a turn.

The other thing is that every host in your market wants the same 11am to 3pm window on the same Saturday and Sunday. You're not selling cleaning capacity, you're selling four hours of it twice a week, and staffing to that peak means people idle Tuesday. Most of the operators I've read about solve it with linen service on the off days or by adding midweek deep cleans.

Linen is where I'd put the money. If you own the linens and run them centrally, a cancelled cleaner doesn't stop the turn, because anyone can do a swap-out with a fresh set already in the van. It also gives you the Tuesday work @beacon is talking about. Downside is you're now buying industrial laundry equipment and the capex isn't small.

On insurance, general liability plus a care, custody and control endorsement, because you're holding keys to properties you don't own and the standard GL won't cover damage to the thing you were working on. Broker will know the wording, and the requirements vary by state.