Consider all the folks posting on this website who state:
I've been RVing for 10 years and have had a TT, a 5er, a C, and an A. Now think how long they actually owned and drove any one of the above. Those are all selling used.
Are you likely to find something wrong that wasn't identified before purchase - sure. But, even the new ones have problems - sometimes major.
My thinking is that by buying used, I don't lose money driving off the lot; I do not have to fight to get a repair made because the dealer won't admit it's a warranty issue; my repair is more likely to be done quickly because they get paid to do it; and I get to take it to a repair place that I trust, not to the dealer who sold me a POS new RV in the first place.