I had bought a used 5vr and it "developed" severe roof leakage. I had to replace 1/2 of the roof. Had two 5vr afterwards, and every year once of twice a year, I would get on the roof, clean it as much as I could, and recalked EVERY seem, edges, around vents and sky lights, and a/c.
Never had another issues with roof - no leaks, whatsoever. Other than scraped a tree limb that caused a little damage than I fixed immediately.
I don't think it will make any difference if you speed $$ or $$$$$ on a new trailer, preventive maintenance and due diligence are the only things that will prevent water damage.
