Unless you’re Brad or Angelina or both or one of the maybe dozen or so actors who "matter" to box office receipts, then pretty much none. You'll go when the director and/ or producer calls you. Otherwise, you'll sit. And wait. And hope. And convince yourself that you're really doing God's work.
You’ll have to take practically every part that’s offered to you, especially when starting out. You’ll have some freedom to interpret the words on the page when performing, but even then you’re something of a slave to the author’s “sacred” text. You’re a puppet minus the strings. And you’ll get paid about as well as one. God help you if the producer’s 3rd wife one day decides she hates you.
Whatever the dream is, put it on a big fat diet to get yourself back to reality. Keepin' it real.