Motor homes are an expensive proposition to start RVing in. They cost more to build than trailers and the used prices reflect that higher initial cost in the used market.
Higher prices doesn't mean motor homes are better built or better quality, just means the cost of platform or frame of the camper portion which is a heavy duty truck or van frame makes the entire rig much more expensive.
Trailers on the other hand can be had for lower cost due to the fact the frame under the trailer costs very little to make.
Motor homes do offer some conveniences like when you stop, you don't have to get out of a vehicle to get into the camper and the camper portion is precooled or preheated when you arrive at your destination.
Motor home do have some downsides, unless you tow a small car behind you, you have to break camp every time you want to get groceries or sight see, leveling can be a chore unless you find one that has built in leveling jacks.
If you have a vehicle with enough towing capacity you could consider looking at a small travel trailer. A bit less convenient than a motor home but also a much less costly way to start RV'n..
The size of Motor home you was looking at, even a slide in camper (AKA Truck Camper or TC) might work for you. Used trucks and TCs should get you in a price and mileage range that might make more sense.
Otherwise, yes, 1980s-1990s motor homes might get you in the price range. Personal motor homes unlike rentals typically will be very low mileage and old ones often are much less expensive.
The downside however, the sitting around may also be a problem with hoses, belts rotting out, pitted and severely rusted out brake rotors and rusted stuck brake calipers, rotted fuel and brake lines and corroded wiring connections.. Along with typical camper water intrusion issues which were not fixed.
