Hi MimiC,
What I would do is check the "For Sale" archives here (in other words, the
sold trailers). While you will not be able to see what they actually
sold for - only the asking price; you will be able to see photos in many cases, in addition to how fast they
sold, which should give you some good info to go on.
A lot is dependent on location and season, so keep an eye out for where and when they were sold.
As far as your sale, I always find a good ad, with a clean trailer, lots of information, and numerous photographs does well. It's discouraging to work with a seller who practically makes you beg for information!
Raya