I’ve got stuck more than once working on chameleon scripts for a fixed fee. As a new screenwriter, you’ll want to avoid that if you can.
For example, I signed onto a project that had Brad Pitt and Leonard DiCaprio both attached to it. Sweet, huh? It was an “Absolute Power” meets “Predator” meets “All the President’s Men” thing, where the President of the United States turns out to be an alien who must eat human flesh at least once a day. Pitt and DiCaprio play the Clint and Dustin roles and Abe said that casting was still looking for a Redford.
But after I’d slaved over the the script for a week, Abe called to say that Pitt and DiCaprio were out and Ben Foster was in. Abe said that Foster being Foster, he’d have to play the crazy flesh-eater and that what we actually had here now was “Nosfetatu” meets “In the Line of Fire,” so that instead of a Redford type, they now needed a new Clint type opposite Foster. On this script I worked a week and went to AA more times than I got drunk, which is rare.
Then Abe calls and tells me that Foster is off the project and instead they’ve got Paul Giamatti. He can’t play a crazy flesh-eater and he’s not right for the President. I know that he was John Adams, but they’re still laughing about that in Hollywood, so no. Instead, the script goes out the window and I have to start from scratch with Giamatti playing that congressman from Idaho who adopted the wide stance.