For what it is worth: My last two trailers were new but two years old, and I never had a problem with either of them.
The last one had a branch come down and puncture the roof, and they were straight up with me and told me that they had put a brand new roof on it.
I talked with the Tech that did it and he said that all his seals were better than what came from the factory.
My advice is find out what a new same model costs and then see if you can get 40 percent lower.I wouldn't worry about the tires or any of the seams. Once you have it you can go all over the seams and my guess is they will be as good as new. If not, just reseal them yourself.
jack L
