I don't think there are many - most ask for money up front, and if you don't have the time and cash to advertise the programs concerned, you won't make a cent.
The best way of earning online cash I've found is to do surveys. It doesn't always pay a lot, but you don't have to put any of your own cash into it.
Those who make a living online are those who are prepared to put all their time and effort into it, not to mention invest some cash. It's not for the timid.