I've been shopping for a while. For us, this is the next step beyond tent camping and a TT will take a concerted effort to use 6 times a year. For that reason we're looking at a TT that will sleep 6 and 8 in a pinch that has an empty weight of <4500lbs. It's a tall order but there are units that fit the bill, from private sellers and dealerships. I tend to shop A LOT before buying so I do as much research as possible before taking a look especially at a private sale. I want to spend as little of a person's time as possible with a private sale vs. a dealership as the sales folks at the dealership are already there specifically to cater to those shopping.
The two big chains near us are Ultimate RV & Camping World. I looked a several units at CW and dealt with two different sales people (I did ask for the first person we saw on our 2nd trip but they weren't available). I liked how everything was organized neatly, was clean and both lots were paved. Both sales folks did a good job of communicating during and after shopping with no pushy sales tactics. Ultimate RV was the opposite, the place was a dirty, unorganized mess with gravel and mud constituting most of their lot. The first sales guy showed me stuff too heavy for me to pull after I gave him very clear specs. He then went on telling me one more sale and he "earns" a vacation trip his daughter is really looking forward to. That was more that a little scuzzy to me. The second visit to Ultimate RV, I was looking specifically at a used (& overpriced) hybrid they had. The sales woman was pleasant and I also let her know my specs, she was much better at showing me a few other units that I could actually pull. After we sat down, it turned to a poo show, very pushy sales tactics and being used I certainly wanted a full inspection prior to anything resembling a commitment. She asked me what my (non-contingent) buy it now price was and wanted me to sign something to take to her sales manager. That didn't happen and I let her know that based on what I saw, they would need to pay me $500 to haul it away in the event there were serious problems. BTW, this was something they hadn't yet taken the time to inspect or clean prior to shoving it onto the sales dirt. Then comes the sales manager, at this point I'm not wasting their time, they're wasting mine. Got the whole spiel about not knowing about what I really wanted without diving in and shopping perpetually means I'll never actually find something. I did appreciate his insight about the last part but it served only to reaffirm, I'll make a solid investment vs. an implusive mistake at least 100 times out of 100.
Both have their pluses and minuses. If you're more indepentant and able to identify and deal with issues, a private sale can save much $$. A dealership will supposedly check everything out and give you a better idea of the condition of what you're purchasing. Some will stand behind it, some will say they will then fail. If you go the dealership route, hopefully you'll not have to find out.