What do you guys think this house could sell for fully renovated(New kitchen/baths/floor/lighting/new central air unit)? 

Eventually our long term goals would be to purchase properties on some of Maine's lakes to Air BNB them.

Town water and sewer, forced hot air heat. 

I think if we continue to see international travel and air travel depressed, people, now Remote Workers,  may care about outdoor space more and a bigger backyard as the depressing concept of a staycation grows in popularity.

Air conditioning units 30 years old, will need to be replaced soon.

I was hopeful to receive some guidance on the best way to underwrite a mid sized multi-unit building (11 Units) with a planned use of Air BnB.

Depending on the zoning change itself it can be lighter or heavier, but I would suspect that if this property was originally zoned for MF then things around it would still be zoned for that, and that seems like it would be a shorter path.Regarding a lack of heat and air . . . that's preferable! 

I am active duty Air Force and stationed in Okinawa, Japan.

I own and operate one Air BNB and I have three night minimum stays.

From a safety standpoint, certain amounts of mold (if I recall correctly: anything over 10 linear feet) require certified remediation (with negative air scrubbers, etc) to avoid cross contaminating the entire property and, frankly, to protect nearby people.