It is important to take your time to look over your car carefully for any existing damage and make the renter aware of the damages before they begin their rental. Damages that are pre-existing are not considered damages the renter is liable for.
In the event the renter causes more damage to the pre-existing damage, it is reasonable that the renter will be responsible and cover partially for the cost of repairs. This applies to each pre-existing damage on the vehicle before the car was picked up if present in the photos and video.