Comps and figuring out the value of properties

[Brady Ascheman]

Hi everyone. I have a potential deal that I am looking into. A real estate investor wants to sell me a 3 plex on a contract for deed. I can kind of negotiate down payment and interests rates to get my Cocr to work. However, my town only has 3,500 people so multifamily does not get sold very often. I am not sure if I am buying it at a price that gives me equity because I have nothing to compare it too. What should I do?