I had the same issue with a past boat trailer - - no
title - so no
license. But - I was able to register the trailer as a home built trailer and got it licensed as such.....
When I
sold the boat and "trailer" - I explained the situation to the new buyer.... and it wasn't a problem.
Call your local DMV and ask if you built a trailer, what information would you need to get it licensed.... Or even call and ask about a non-titled camper - I'm sure you're not the first to ask this question.