I bought an unregistered boat with untitled trailer in VA. To register the boat in NC I had to have a notarized bill of sale, I also did the same thing for the trailer. The trailer was more complicated but basically just involved filling out lots of forms and taking out an indemnity bond for 1.5x the value of the trailer (of course the smallest indemnity bond an insurance company will sell is $10K but it only costs $50). The biggest hassle was that each person at DMV I talked to (I went there 4 different times) would tell me a different thing and make me fill the forms out again and even go to a different DMV location, which was not simple since the insurance agent had to sign everything again too.