Lionhead Studios has revealed that Fable Legends will be free to play, using rotation models of other games like League of Legends.
There will be four characters you can play in rotation, and in any one time some of these characters will not be available to play. You can pay to unlock them permanently, or you can just wait it out until it rotates and you can play them again. You will also be able to buy cosmetics.
Furthermore, you don’t have to pay with actual money. You can earn in-game cash for these cosmetics.
Fable Legends is in a unique spot here, but this monetization model has been proven to work on PC, and apparently Microsoft has found it successful in Xbox One for Killer Instinct. Fable Legends will be on PC and Xbox One, and will offer multiple cross platform functionality, including cross saves and cross platform play.