They wanted the buildings repainted, signage removed, tree removed, windows fixed and various other things.

Reasonable is always on a sliding scale though, I know.

If I were you i'd toss the wholesaling plan out the window.

Another option is the Combo window/wall mount heater/AC.  

Look below this Window, and you will see a list of names of people that have posted in this thread.

I have a checklist I walk down each visit to look at plumbing, locks, smoke detectors, windows, pests/mold, overall condition, pets, etc.Scheduling them is the biggest pain.  

When this happens underwriting will tighten up and will not allow things they may have been able to slide just a year or 2 ago.5 years ago many insurance carriers would write these properties from day one without an inspection.   

I plan for a minimum of $2k for code inspection work- sidewalks, window locks, trip hazards, maintenance issues (basement wall sealing, exterior brick work, painting exterior trim on windows, screens, and then all of the expected- plumbing, HVAC cert, chimney cert, electrical,  and on and on.)  

Most window suppliers will have limiters that keep the windows from opening too far.

Both 4 BR, 1700 sq ft, finished basements, split AC on 1st floor and I provide window ACs to BRs.