How to Comp Vacant Land? (no MLS access)

[Blaine Alger]

I have an infill lot that I am looking at in Waco, TX. It is in an up and coming area that is seeing a lot of new development and builds. The home prices in the are are a little all over the place due to the fact that it is gentrifying but I would say a builder could come in a build a 200-350k house. 

They are asking 85k cash and I would end up assigning the contract to a developer if I were to lock it up.

My problem is, i'm not sure how to accurately pull comps for vacant lots and don't really know what price point I need to be at.