Welcome to the group. Have you tried the classified adds
here? You might just get lucky. Everybody here will tell you the same thing, look at lots and lots of trailers. Maybe attend a local rally and see what size and floor plan you like. Also use the search function as a tool. A better search is from google. Enter "trailer inspection site:www.airforums.com" and you will get a pretty good list of threads containing the words "trailer inspection".
As for model year I would suggest staying in the 10-20 year range unless you really want a project. Nice trailers are out there, but sometimes a little hard to find and are long way off. Conversely you will also encounter money pits that are younger than 10 years. It all depends on trailer location and PO (previous owners).
So hunker down, start looking, and keep us posted on your progress. Also be aware that if you find a trialer that is a little far from home, there are folks on the forum willing to do inspections for you, if the trailer isn't too far away for them. Check out this thread...Need A Volunteer Inspector?