It's a cool concept but KM is right, it's very naive.
Abandonned buildings can be structurally sound and safe, but left unmaintained for so long, it's completely unpredictable how they would have faired.
The cost alone of having so many buildings structurally evaluated just makes this completely unfeasible, unfortunately. $145k would get the project nowhere. All the buildings in a proposed area would have to be evaluated before the area was purchased. The cost of maintaining a safe environment would also be ridiculously high that it could compromise any sort of profit margin.
The only feasible way this could really get off the ground is if they started with just one large building, a factory or something of the like that was structurally sound, convert that into some kind of airsoft arena, and then if successful, eventually expand further, buying up pieces of land and more buildings as they went along. It would still be pretty abysmal as far as 'business' sense goes.