Is there a way to make it to where players need scrap to spawn the mini?

If you want players to buy vehicles, you can try the Vehicle License plugin, but it is a bit more complicated so might be harder to set up. You can also integrate Spawn Mini with a GUI plugin to call the server command to spawn a mini when a player makes a purchase, but afaik that sort of model has issues such as they could double purchase it and not get another if they already have one.