I saw these in Deltaville, Virginia a couple of weeks ago. They look to me like trailers on pontoons. I asked, and they're visited regularly by a pump out boat.

I just don't see the point. Why not just buy a boat for a liveaboard, something with a pointy bow? That's what I did, lived on it for a year and a half in Stamford CT. We're now in Beaufort NC and slowly making our way south. I just can't see any of these trailer boats dealing with some of the conditions we did. Of course, I guess they're designed to stay put.