Yes, you can. If you rent it for the day, you can paint whatever you have to paint.
If you have 2 cars to paint, you can do this, but of course you must be able to get them done within the alloted time.  Doing 2 cars will be pushing it for most though. If you had the cars outlined in tape and had them completely ready and you are efficient, you can get 2 done.
If you have motorcycle sets, I’ve painted a few all at one time. You can pretty much fit about 15 parts in the both.