Here's a thought that may work for you if you have the time and a place to do the work...
Buy a cheap Class C on a good solid frame with good running gear (engine, tranny, etc). Doesn't matter what shape the RV section is in because you are going to rip that part off and make a new one. Save the windows, the skin and anything else you want. Take all the way down to the chassis frame. Rebuild it. I can tell you for a fact that the 1976 Midas Mini Class C that David & I lived in was made from 2X2 pine that was stapled together. You can do that. Probably easier and faster than buying a skoolie and stripping it out then rebuilding it.
If we had a place to have done the work (and the Class C had been a little longer than the 22 ft it was), David & I probably would have simply rebuilt the Class C or a different one. We would have made the floor, walls & ceiling thicker to add more insulation. Eliminated the front window in the cab over (it's a leak waiting to happen) Probably would have used metal studs that were available back east (not here) to lighten the load. Made a slightly bowed roof to eliminate the ponding that kills RV roofs. The interior would have been done to suit our eclectic tastes. And there would not have been a problem with insuring because it would still have been an RV and we would not have changed the title in any way. An RV that is not to manufactured RV standards but to your standards. If you keep the floor plan about the same, you should be able to reuse windows and skin. Watch the metal skins, the aluminum ones can get tiny pin holes in them. But an easy fix. Simply prime (latex aluminum primer) then paint (latex house paint in semi-gloss) the metal skin, then embed ordinary bed sheets or similar thin fabric into the wet paint, smoothing it out so there are no wrinkles. Let dry. Cover the material with at least two more coats of latex paint to create a very durable coating. Put the metal trim back on the corners (use butyl caulk under the metal trim or use clear elastomeric roof caulking).
Many years ago David used to work in a mobile home manufacturing plant in MI near Elkhart IN. Some of his co-workers used to work in the RV manufacturing plants. They told him how the things were built. The walls were built laying on a concrete floor according to a guide painted on the floor. That is why the staples are only on one side of the frame... the side that was facing up. The RVs are build like manufactured homes. The whole thing is built from the frame up... all the flooring (including vinyl, carpet) is in place before the walls sit on top of the floor, then the roof is placed on top of the walls.
Want to buy an old 22 ft 1976 Midas Mini Class C? GMC Vandura 3500 chassis (what all the motor/running gear parts are). The engine (carborated 400 or 440 - I forget which) is good just needs an electric fuel pump as the mechanical one is shot. The automatic tranny was rebuilt and works great now. Has rust issues around the windshield (not leaking though). But if you are tearing the back off then popping the windshield out to fix a little rust would be simple. I've had the thing up to over 80mph on the interstate so it can run..... See, this is a good example of what you could expect from a manufactured Class C. Just assume everything inside would need to be replaced and base your buying price on that. Low ball and you will most likely end up with a good deal. A Class C like I just described could easily be bought just to get it hauled off. I would love to get $1000 for mine. It has an LP/AC 6 gallon Atwood water heater bought in 2006. The water pump was replaced in 2010 (but a pump we had tucked back for replacement). The refrigerator is a dorm style and the freezer is an undercounter style. The furnace needs to be taken apart and cleaned but it's good on LP use. The rooftop AC is from 1986 and still working well. Or was last time it was used. The all-in -one bathrooms like what I have will most likely need a new toilet. That is because all the water causes the metal parts in the toilet to rust then break. We found that we could buy a new toilet for the cost of replacing a few parts that had rusted. Instead we devised a work around. Kinda like the awning. Cheaper to replace the awning than it is to buy a new part. If you get an RV that has the metal cover on the awning SAVE THE METAL COVER!!! That is called an "Alumi-shield" it will keep your awning in one piece much longer. On ours, it seems to help keep the fabric awning material from being destroyed where it attaches to the RV wall. Not sure but I have looked at the ones that have the shield and the ones that don't. It just seems the shielded ones are lasting longer. If you can use some parts, wonderful. If not, that's okay you bought the RV cheap enough to replace everything inside it.
