[Abagail]

You can use enumerators to store it's data along with a data system such as MySQL to save the dealership data. You then can use a command processor such as ZCMD to make commands such as /dsinfo, and /buycar. It's really
not a hard thing to do. You can find example scripts below,
https://sampforum.blast.hk/showthread.php?tid=299738
https://sampforum.blast.hk/showthread.php?tid=518564