It's free (and just takes a few minutes) to register with any of these auction companies. Lots of good stuff for sale, from used pickups, trailers, service bodies removed from trucks, deisel trucks and busses, etc.
maybe you should look at Park Model Homes. living room,full size kitchen, one bed room. Ck out Texas "Cavco's Family of Park Model Brands"
Because these are over 8' wide, they require a pro driver to move. With a tiny House or a travel trailer, you could move it with a rental truck AND move your storage stuff while you're at it. Just because of the size and the full-size appliances inside, chances are they are going to be a lot more than $20,000. I want to be a bit more mobile than that. Otherwise, they seem nice, though.
2005 Jeep Wrangler Unlimited (LJ), silver w/black top auto 4WD - Scout Recovery Vehicle
1977 International Harvester Scout II, red w/white top manual 4WD - Jeep Recovery Vehicle
Instead of a park model, if you were going to have a trailer parked at one location for a long time, a "destination" trailer could work. They're sort of half way between a full-blown park model and a normal travel trailer. Not something you'd want to drag around constantly, but with more space than a typical travel trailer, with higher ceilings, residential-type applicances, etc. all in a 8.5' legal width with the slide-ins in.
It's better to regret the things you've done, than the things you haven't.
Just buy an old skool bus and convert it how you please,tow a rig and use the bus as base camp.