Owner-managed subs on a 64k rental rehab versus paying 18 percent for a GC

The honest way to split this is by who eats the gaps, and hours on site is the wrong measure of it. Think about what the 18 covers. A tile crew arrives and the drywall is not ready, so someone has to have that conversation and then find the crew another slot in a schedule that is already full. A panel upgrade fails inspection on a detail, and someone has to get the electrician back without paying for a second trip. A discontinued vanity has to be replaced inside an hour, not a week. A good general contractor absorbs all of that. You will still be on site, but the time goes into looking at finishes instead of untangling a scheduling collision at 7am. A weak one absorbs none of it, and then you have paid 18 percent to make those calls yourself. So the real question is about this specific person and whether he does that work. Ask him who his site lead is, ask for two investor clients he finished for in the last year, then call them and ask what the last thing to go wrong was and how he handled it. On the drainage at the back corner, get that scoped separately before anything else starts. Water is the most common reason a $64k rehab turns into an $80k rehab, and you want a price on it before you are committed.

One thing worth pricing out before anything else is the licensing question. Depending on your state, pulling permits as the owner on your own rental can be limited or come with conditions, and some jurisdictions treat an owner-builder permit differently from one pulled by a licensed contractor. That varies state to state and sometimes by county, so call your building department and ask what they'll let you pull as an owner on a non-owner-occupied property before you assume the self-managed path is even open.

If they'll only issue to a licensed GC for the panel and the drainage, half your $11.5k saving disappears into hiring a permit-holder for those pieces anyway.

Take a smaller version of this, about $38k, self managed, and the framing shifts. The hours are rarely the expensive part. The expensive part is that an owner doing it the first time does not know what good looks like, which is how approved work turns into a rebuilt shower pan at full price. @tonyv88 is right that the 18 buys somebody to eat the gaps. It also buys somebody who knows when a trade is walking off a bad job. On a first rehab of this size, that is worth more than the scheduling. On a 10 week job with a real job on top of it, the sound move is to pay the 18 once and watch how he sequences it. Then decide on the second house.