I'm pretty sure that we have bought our last one first. It has been 7 seasons & nothing that we would rather have has been seen.
We did the research first. We narrowed the field down to 3 or 4 models. All had to fit the same criteria for quality of build, tankage & similar floorplan. New was under consideration only if almost new could not be found.
We bought almost new, 6 months old. We bought somebodys mistake. They thought they would like RVing. They hated it & wanted out having just closed on a new very nice house. Helped them move their stuff out of trailer straight into their house.
Nothing wrong with buying quality used.