I have 3 fourplexes with basically 900 sqft apartments.My "rehabs" so far are basically re-paint (walls, not trim), do minor repairs, replace carpet w/ LVT (about 650 sqft), replace carepet on stairs, and replace the countertops w/ pre-fab laminate tops from big box hardware stores.Materials and labor come in around $4500/unit when I do that. 

But do you want your tenants putting holes in walls or trim to hang blinds?

My largest renovation, which was NOT a gut flip, but had some foundation issues, did NOT need hvac work, or a new electrical service, or new plumbing, and I did a bunch of the work myself (cabinets, trim, paint, tile...) comes out to $63/SF.

We just framed them in with 2x4s and trimmed them out.

Most of them were silly stuff like paint windows and trim, restore down spouts that kind of stuff.

Replacing with drywall, bamboo floors in the kitchen and family that lacked wood, and all new trims, etc.

First I had a friend who owns a glass company build thermopane frosted glass to my dimensions, I then routed and built a complete frame out of PVC trim, if you notice, I made the inside ledge very slim so less water lays on it and people have no room to be storing bottles and other junk on it.

If the answer to question 2 is no, trim it.

I have also picked up afew lots with scrap mobiles on them and lots of junk that I got because I had heard about the pig stys in a nicer area these were crap at lake eufaulaI contacted lots of owners and in some areas they won't allow mobiles anymore and neighbor were happy I bought Let junk collector I know take anything he wanted and he took everything even rotten lumber I did have to pick up some insulation and afew other odds and ends and had it mowed trees trimmed

He posted another note saying that the trim paint is peeling and has to be repainted :) The house is actually in a better condition then my own home.