Here's another angle to consider.
If you want to attract serious and successful sales people, give careful thought to "lifetime commissions". That is, the referrer continues to make a little bit each month, for as long as the clients they refer keep their accounts with you open.
This turns the referrer in to a real partner, and gives them a reason to make the investments that are necessary to be an effective rep for you.
I know of one hosting company (sitebuildit.com) that was built in to many thousands of users specifically by this method.
I've known one of the leading affiliates for that company for ten years, and he worked his butt off for them, specifically because of the lifetime commission. He is now semi-retired, living comfortably on these earnings, because the many accounts he sold are still open generating revenue for both host and salesman.
Here's the real deal. 10% of your affiliates will produce 90% of the sales. The top people are the ones that matter, and you really want to give some thought to what it will take to attract them, and keep them happy.
The great majority of your affiliates will never produce any significant sales, no matter what you pay them.