Originally Posted by kane

There have been some programs in the past that did something I liked. You sign up and get a bonus based on the number of sales you send. For example, once you send 10 signups you get $100 bonus, once send 50 singups you get a second $500 bonus and so on.

It wouldn't need to be ongoing. You could just say, "after you send (insert number of signups) we will give you a bonus of (amount)."