I've done some searching and couldn't find much info on this subject. If you were to hire a musician (be it a keyboardist, cellist, whatever) to perform with your group at gigs, how exactly does it work? If they have a large list of songs to learn, and need to rehearse, I would assume that they charge for this. Is there a certain way it's set up? When they get paid, how much, for what, etc. ?