It’s more of a visual impairment then a structural.

- What is the soil condition, and will it require any special treatment to be suitable for building?

The first thing to know about crowd funding solutions is that many are structured in a way that they would not qualify for 1031 Exchange treatment (e.g.,  membership interests in a limited liability company that are treated as partnership interests).  

Ask yourself all of these questions snd write it all down so you can visualize everything.

I can see why they gave it good marks on visual inspection.

@Daniel Overby Ozone treatment for sure.

Or some other form of treatment?

This is the snippet from the Massachusetts standard Purchase and Sale agreement that outlines the treatment at a high level.

I love your illustration of the "baskets" , such a simple way to explain in a visual way. 

I'd pay the first round of treatments, while informing them (and have in lease) that they will be responsible for future costs of pests as motivation to keep the place clean.