I'm not as experienced as most around this forum, but I have learned some lessons -enough to know that what these guys are saying is spot on. Things like, suit your lifestyle, etc. but you could still get it wrong.
For example, we thought one of the dumbest things in RVing is that just about every RV we looked at (within our budget) had the television at a right angle from the sofa/theater seating! Dumb! Unless you think everyone wants a crick in their neck! That was a big deal to us so we looked and looked and found one we liked with the seating directly across from the TV. Well, guess what? Turns out we don't watch TV when we're camping! Ever! I'd of rather had an outdoor kitchen. We may watch a movie on the rare occasion the weather is too nasty to sit outside but still we mostly play games, cards, etc. So, think about stuff like that.
WildeBill made a great point about being able to get to the head and kitchen, etc. with the slide(s) in. That was a must for us when we bought our new one. You can save lots of time (and money) when you're able to just pull into a roadside and sit down to a meal right from your own kitchen without even having to let out a slide. We always had trouble getting lunch on the road pulling the 5er and the fact we always have our not-so-friendly-and-not-meant-to-be dog with us made it more difficult. Now, easy peasy getting lunch in the coach -we did that on the trip home from the dealership and it was such a relief!
Like John, I prefer to buy new. But, from my experience, your first RV is rarely your last. Neither is your second, third, . . . :~) But seriously, something else you have to think about and decide.
Finally, we also read some terrible things about Thor -I'm not saying we know it first hand or have any personal experience with Thor, I'm just saying what we read on line over and over. So, we steered clear of Thor.
Good luck with your hunt. That's part of the fun!