Usually, the way it works is, you as a producer have your own "contract." A completely basic lease, they would just get an mp3 and if you're doing it manually, you would email it to them. A premium lease, they would probably get a WAV file because its higher quality, along with rights to use the song more. An exclusive, most commonly, you give them the WAV file through something like dropbox (a file sharing website) along with ALL of the individual patterns you used to make the beat in WAV form so they can mix and match it themselves. That's called giving them the "tracked out" version but to suggestions: one, based on personal experience, do NOT send anybody anything (unless its a tagged demo) until they pay you and two; go to myflashstore online. You can set up an account where it will automatically sell your beats. You dont have to do anything but upload them and promote it. I personally use rocbattle and soundclick but most consider myflashstore to be the best.