Here in NC all you need is a bill of sale to transport the vehicle. You do not have ot have the title. For example: earlier this year I bought a used pop up camper from a private seller. They typed up a bill of sale (no official state paperwork necessary). I left with the camper and took it home. This happened on a Saturday afternoon. On monday I met them at a bank and we had the title transferred over (notarized) as well as notarized the bill of sales (each of our copies). You do not have to have the bill of sale to register the vehicle here if you have the title. I went to the DMV to register it with the title and that was that. Same thing when I bought a utility trailer from Lowes. Lowes had the title and a notary there. The sales slip (bill of sale) was all I needed to tow it around. You have 30 days to get it registered. Bill of sale is your registration for that first 30 days.
