No, floor rot and inner wall damage is a main topic on another forum that I belong to
http://groups.yahoo.com/group/scampers/?yguid=351957258
While not as prevalent as in 'stick built' trailers, it is still a problem with the 'glass houses'. There is a certain amount of wooden ribs between the walls. The main points of leakage in a fiberglass trailer are around roof vents, windows, seams, around the door, and where the body meets the floor. Also, condensation build up will flow to the lowest point, hence the floor rot, not to mention leaky pipes, etc.
I did not mean to say that all fiberglass trailers have this problem, just to say that it, like any trailer for sale, should be inspected thoroughly. This may well be a gem, and I hope it is.