Every time this client buys from me, you get 10% of their invoice fee. 
Payments come quaterly, via bank transfer or Paypal. 

Once you are set in the system, you get a specific page to give your people. They fill the form, get tagged in my system and I will know they come from you. 
Once a deal is made, you get an email to let you know and payment follows once their payment has gone through.