I have built a few and sold a few. Be sure all the numbers the seller is providing match up. Make sure it is operating in the green. If you are going to have a mortgage you need to take that payment into consideration also. Have survey done. Make sure that the septic and water systems were put in with permits and NO violations. Health dept can shut you down real quick if something was done under the table without a permit. Health dept. should have a record of the systems if it is NOT on public sewer.Make sure all licenses are up to date and NO sales tax violations or state revenue violations exist.