Mobile Home, Off-Highway Vehicle or Vessel. Motor vehicles, vessels, mobile homes and trailers must be registered at the point of purchase and a certificate of title issued as proof of ownership.Registering a trailer in Florida requires a Florida trailer bill of sale form. A completed form to title and register a trailer is required. Additional Resources. This document serves as proof of ownership and allows the seller to report the sale to the DMV. The form includes the details of the vehicle.