it works for whatever you like, as long as you own the rights but i think you are more likely to sell songs than beats, but you could do some beat ep's or albums, mine and Memento's album is an instrumental album. You cant really use it to sell beats to rappers, thats best done through networking really, and thats a grind of its own. But once its up on spotify at least people have a place to check out your music. I also use soundcloud for a quick upload, and youtube, after Ive made a quick video for it.
Im still on reverbnation but havent used them for years, but they are always sending me opportunities by email.