Some sites like VRBO and Amazon have rules that won't let you post a review if you never used the product or service, makes sense on the surface.

Without knowing more about the deal I can't give you the best advice but on the surface it definitely feels like it has some potential.

Unless its surface mold that can be sprayed/ozone machined, drywall is porous and needs to be replaced. 

The surface of the roof is ~5500 ft sq, and the building is in a cold climate (nice summers, snowy winters). 

Horizontal, surfaces, door knobs, high touch areas, etc.

I install hard surface flooring (Vinyl plank & Tile) in all high traffic areas and wet areas.By installing carpet in only three bedrooms, the cost is minimal to replace if necessary in the future.

I just negotiated  11k off a solid buy and hold rental house in cedar park and I helped navigate my client through a myriad of bad choices (which seemed on the surface like good deals) and multiple offers situations.

Every one has there own opinion, but 10% does not even scratch the surface of whats about to happen.

I realize it’s not likely to cause an issue with neighbors or the city on the surface, but I’m curious about potential liability issues. 

But to answer your question at the surface level I would say it’s 100% ok to start with any of the units or locations you stated.