Automated Vehicle Despawner, can't find any tutorials and tips?

Hi, I'm trying to make some sort of auto vehicle despawner for my game that, suprisingly, will have vehicles involved. These vehicles will be using A-Chassis by SecondLogic.

Anyways I have been scouring the world wide web for any tutorial on it, I can't seem to find anything. I can find similar concepts but not what I need. For anyone confused I'll explain how it works. Once someone hops out a VehicleSeat, the vehicle takes 20 seconds to despawn to avoid clutter and ingame lag.

Also yes I'm new to scripting, I'm just browsing tutorials to get the hang of things. If I can find an example of it I will link it in the comments.