Most states require that all trailers, of any size, have current licenses and registration. Some states do not require titling of certain trailers and vehicles, but it is generally a good idea to exercise a bill of sale, or a title exchange, for all property transactions.
For specific state requirements the Department of Motor Vehicles, the seller should consult the state in question. Failure to title a travel trailer in a state that requires it can result in a penalty or fine. To title a trailer the state DMV generally requires proof of ownership, such as a signed title or bill or sale, personal property tax receipts and, in some states, proof of insurance