They are smaller than a Class A (usually a bus-type or a fifth-wheel motorhome) and bigger than a Class B (usually the size of a large conversion van). It is built on its own chassis and driveable, but it's the perfect size.
Me? I prefer the travel-trailer. You can haul them around on a van or pickup and use the van or pickup to go into town. The travel-trailer is big enough to sleep 5 or 6 but doesn't have the bulkiness or drag on the highway as a fifth-wheel. But a Class C fits the bill too.
I get combined 15.1 mpg towing it with a Toyota V6 from Lake Tahoe to the Arizona high country and back. There's lots of rolling hill desert and some serious uphill climbs/descents going both directions. I have a manual transmission and wouldn't have it any other way.
Randy, you seriously ought to consider and compare a lightweight travel trailer rig against a Class C. If you truly need something heavy like a Class C, I merely recommend diesel power.
I know several people who have given up their houses and moved into an RV year round. Younger, working ones. They’re very comfy and do well for full-time living. And, much better than an apartment. And, if you don’t like your neighbors, you move!