There are 2 common models for affiliate marketing:
Pay per join and revshare. With the first the affiliate gets a one time payment for someone joining - note that this payment is usually much higher than the initial sign up price for the website. You may have a site where the customer joins for $1 but the affiliate gets $80 per join payout. The idea is that the program will make money on automatic rebills.
In revshare the affiliate gets a percentage of every sale the customer buys on an ongoing basis.
Pay per join and revshare. With the first the affiliate gets a one time payment for someone joining - note that this payment is usually much higher than the initial sign up price for the website. You may have a site where the customer joins for $1 but the affiliate gets $80 per join payout. The idea is that the program will make money on automatic rebills.
In revshare the affiliate gets a percentage of every sale the customer buys on an ongoing basis.