I wanna let people spawn their own cars but only 1 at a time.

When they do "/spawncar" they spawn a car

If the player already has a car spawned it will say something like: "You already have a car spawned and can't spawn any new cars. Delete the old one first by destroying it." And then that the cars will also destroy when they get into the water for example.

How do I do this?

I'd love that option too. Also, an option to allow driving cars underwater. The plugin's author doesn't seem to be answering topics here on the Help section. The UI isn't showing, /clearcars isn't working, etc. Unfortunately, the plugin isn't usable right now.