Quality!! They were well built for the rental market but also have their issues, which are fixable but can be challenging and frustrating. If you are interested in buying one I strongly suggest that you join the Uhaul
facebook group (you have to be accepted by an administrator) then in the "files" section at the top of the page is a thread about "common problems" that has good information about what to look for or expect. Lots of good info in the files. Owners and repair manuals plus parts info, also found in the document section here. There are trailers out there that are in very good condition, some not so good, and many have had modifications and upgrades so it's hard to make a general statement about their condition after 30 years of use, (and rental abuse).