I guess it depends on the condition of your car. I've had a vehicles in several movies filmed here in New Mexico. The first was a student film "La Otro Ves" which I gladly let them use an' 73 Ford Econoline van. The kids didn't know how to drive a stick, let alone three-on-the-tree, so fortunately, an adult instructor did the driving, although later on, I did some drive-bys for them. We didn't do a contract for this one.
The second film, "A Lonely Place to Die", an independent film, the producer had a four page contract for us to sign, although I don't think that they ever used the van.
The third film, "Love Ranch", the production people actually bought our car, a '1974 Lincoln Continental Mark IV. It was sent to a customizing shop and turned into a Bugazzi. Our car was one of three Mark IVs that they bought, although the first one ran so badly that it was never used, so it was our former car that was in all of the New Mexico scenes. They also used the same Econoline van as a background vehicle. It did make the final cut and can be seen towards the end of the movie. For the van, they paid us for the use of the van, plus costs to get down to the set, a 200-plus mile round trip!
Below are photos of the vehicles including the Mark IV after it was converted to a Bugazzi, along with me in the Bugazzi.