For what it's worth I have only had truck campers as well. I narrowed it down to Arctic Fox, Outdoors RV, and Wildcat Maxx by Forest River. All 3 have similar construction ie AL structure, radius roof, 1.5-2" thick walls, enclosed under belly with heated tanks for 4 season use, and a GVWR of 11,000lbs (ish). All were made in Oregon which was one of my wants and all had an "RLS" type model.
#1 was ORV but the 24RLS is new and there is no used available.
#2 was an Arctic Fox but there are not many newer used (read as 2-3 years old). Lots of 10-12 year olds but that is older than I wanted.
#3 was the Maxx and we found a few within 400 miles of us. Ended up getting one that was 3 years old for a decent price.
Speaking of prices, you have to do what makes sense to you and prices are all over the place. We had found a great deal on CL but the guy took forever to return calls. We were not going to drive 300 miles and not know if he'd follow through. We went to look at one closer to us at a dealership even though the asking price was way out of our budget. They wanted to talk price so I told them what I was willing to pay which was a pretty low offer compared to asking price. To my surprise they got within $750 so the deal happened. They came down over $12K from their asking price on a 2015 27RLS that was equipped exactly what we wanted.