Best way to look for quality is to remove the bulk head to the basement. If the wiring and plumbing are neatly run and secured every few feet. You can assume there was a certain amount of quality built in. If you see wires and plumbing haphazardly slopped around to and fro, basically a rats nest, and not secured you could assume the quality is not the best.
The best example I have ever seen for quality was SnowRiver truck campers. They even took a small marking pen and wrote what it was for on the wires. Have pictures of that stored some where. Unfortunately Bob and SnowRiver truck campers are no longer with us.