Mobile Home, Off-Highway Vehicle or Vessel. The form also documents the sale and is the legal receipt.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. 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. How do I fill this out? To fill out the Florida Trailer Bill of Sale, gather all necessary information about the seller, buyer, and trailer. An RV Bill of Sale is a legal document that serves as proof of the sale and transfer of ownership of a recreational vehicle (RV) from a seller to a buyer. Use our free Florida bill of sale form in order to legally buy or sell personal property like vehicles in the state of Florida.