if I were doing what you are I'd look for an old RV so that you have water tanks (both fresh and holding) for the sink and toilet (which will be nice to have), plus it will have propane for the stove and a furnace which it will likely have. Most have an air-conditioner but may require 120v, so look for one with a generator. I'd bet you can find one from the 70's for the same price as a bus and require a heck of a lot less work to have all the amentities.