This one is different from Affiliate Marketing in that you earn a commission if the customer does an action. So you don’t have to make a sale through your affiliate links, but you must get people do an action.

The action could be subscribing to an e-mail, install a mobile game, subscribe to a website, taking a poll or something else. When they do this you earn a commission.

The upside is that you don’t have to sell anything.

A few CPA networks:

CPA Marketing