I am just curious to know a little bit more about your problem. I currently have a problem with an odor getting into my basement that I think might be related to dampness of the ground. The problem only occurs when it rains. What is a vapor barrier on soil surface? How do you know if the the ground under your house is wet or dry? You might look at webiste http://www.extension.umn.edu/ for information on basement moisture problems. I would be very cautious about purchasing this house. Installing a drainage system could get pricey.