You notice in the ad Techie linked, they call these things "RVs". That gets them out from under HUD rules and until you actually take the wheels off and hard wire them to the utility, most building department rules. When they set this thing in a trailer park near me the park owner was mad at me because I insisted they get a permit and a real electrician. Most of the units in there were installed by the park staff, without any permits.
This was a 362 square foot unit and I think they only paid $18,000 for it. Those Tumbleweeds seem very expensive.
