Any ideas on how to approach the used market?
Educate yourself first, there are great deals to be found with research and most of all patience. A lot of people buy them, use them once or twice, it sits for a year or more (too long is very bad) and decide the RV/TT life is not for them.
There's a notice on the bulletin board of one for sale where I work - sign says "never been used".
Read RV.net - RV.Net RV and Camping Forum ? RV, Trailer, Camper, Motorhome, Camping and Campground Information. There's a lot of experience and knowledge there and they're happy to share it.
Unfortunately I have not yet been able to talk DW into buying one.