The true way to assure valid funds is a wire transfer to your account. Checks of all types can be forged and cash can be counterfeit. Many states are starting to require all real estate transactions through title companies be conducted with wire transfers of funds.
There is a questionable period in all transactions where the title has been given to a new owner but not yet transferred. Dealers have the same problem and their insurance takes this period into account. Do not cancel your insurance coverage until you feel confident title has been transferred. A common mistake is for the owner to allow the purchaser to drive the unit home on his tags. NEVER do that! Temporary tags for this purpose are available from the State in every state.
Making the actual "closing" in the environment of a bank or credit union is a very wise move. There have been many a mistake and unfortunate happenings with vehicle transactions not conducted in a safe public place with knowledgeable assistance available.