calculate Land offer

[Natasha M.]

I'm really new. I haven't done a wholesale deal before but I understand how to analyze houses. However, I have 3 FSBOs in the Baltimore Maryland Suburbs who want to sell their old house/land. One is a possible tear down. one was torn down due to a fire, and the last house was built 1900 and is currently being rented. Together they have over 50 acres of land combined between the 3 FSBOs. 

I want to help them rid of their property but I don't have the $1,000 to pay an environmental engineer to give me a report on each property to forward to a new developer.  I have determined the zoning & about how many subdivisions can be created on each property. How do I go about calculating a fair offer so I can wholesale them, or even just bird dog to a new construction developer?

I'd appreciate any suggestions