For every brand & model line someone posts that is poor quality and you should stay away from, there will some with the same brand & model that say that they've never had any issues with theirs. Some are willing to accept substandard quality or don't recognize it. Some just fix things as they need fixing and think it's normal in a TT. I could post a couple of brands to stay away from, but won't.
A better question might be which brands & models are above average in quality. Lance, Nash and OutdoorsRV come to mind. There are some others in this category. TTs all use the same appliances & components so after the warranty expires, it's the initial build design and quality that is the question.
I'd stay away from a TT that has I-beams in the frame that are made from 3 pieces of steel welded together because they flex a lot more and can cause various problems. Look at axle and tire ratings and if they are loaded to near their weight capacity, I'd pass. (Take the trailer's GVWR and subtract 12 percent of that as estimate of weight on the tires & axles).
Before you hand over the cash, you might consider hiring an independent RV tech. to do an inspection.
