Marketing a game.

Ok, well I was wondering if I created a game such as the ones you see in the "Game Downloads" section would I be payed based on how many copies where downloaded or would I only be payed if I was too charge a player say $5.00 USD too download the game based on an ID system and then I would receive like $2.50 USD for every copy sold? I am new to marketing but a general elder in the programming business I usually just work with a team on games not create my own.

Thanks
Josh