Most of affiliate programs that I have reviewed have referral program. You can have more than 2 tier affiliate program where you make money also from webmasters that were referred by your referrals or it can go deeper. So there are n tier affiliate programs (multi tier affiliate progrmas) which pays to many levels. For every level is diferent % for you. You can earn money very fast if you refer lots of friends and they refer other friends. Pay-rates are usualy from 1$ up or you make some % of your referred webmaster earnings. So if he make 1000$ per month you get 100$ every month!!