Officially, once your hands touch the keys, you are responsible for the car and avis will not allow parking of the car on the avis lot for liability reasons. however, unofficially, it has been known to happen. Much of it depends on the size of the location, space the location commands, among other things. I rarely let customers park on my lot for even 1 hour, let alone overnight. But I do point them to a lot off airport that is a slight walk from our location that no one knows about.