one of vaughan's sources of income right now is that he's leasing the film rights to y: the last man out to (I think) the third or fourth different production company. as it was explained to me, the film rights are bought out for six-month intervals, and if actual production hasn't begun by the end of that, the property reverts and brian still keeps his money (which I'm sure is still chump change to big-name studios).
This is called an option. Smaller production companies who can't afford to buy a book's film rights in total instead option it with the upfront money usually being considered the down payment on the full, already agreed upon final price for the rights. They have a certain amount of time to find a larger production company or a studio to agree to a film and shell out the money needed for pre-production as well as the rest of the price for the rights. If they can't get the rest of the cash, the rights go back to the original owner unless an extension is agreed upon. Any work on scripts, designs, etc. that the option owner pays for is theirs and remains in their control even when the right revert back to the source's creator.
This is also done with spec scripts.
