Didn't read everything, but a few things to look into.
Cooling system - is it a chilled water system? 2 pipe or four pipe? Air cooled or water cooled condenser? Split systems? Age? If it is a CHWS and not being maintained replacement costs can be huge, especially if underground piping is decaying, it would me cost effective to replace with DX Splits.
Heating - they mentioned boiler and hot water heater replaced in the last 10 years. If it has boiler and CHW definitely find out if it is 2 or 4 pipe.
Utilities and RUBS - I gathered from a comment or two it was all bills paid. Is that typical for your demographic? Check to see if utilities are individually metered like the electric and water. If not is there currently a RUBS system in place?
81% Occupancy - Is this physical occupancy or economic occupancy? Just becasue 81% of the doors are full doesn't mean 81% of the doors are paying. Why are the remaining doors down? Differed maintenace? Poor management? Lack of bodies (detroit has suffered publicly)?
Anticipate a guestimate of 3000-4000k per door to get a base rehab done in that demographic, and would not include roof, mechanical, structural, exterior. While there may or may not be a deal there, if you are just getting started you will have a huge learning curve to get through. If you're fond of having time and money coming into your account and not flooding out, you may want to reconsider. If you'are up to a big challenge and don't give up in a fight, as long as detroits economy can support this property, after you stabilize the asset you might have an upside
my .02