Assalamu alikum,

Islam Question and Answer - Commission (http://www.islam-qa.com/en/ref/21980/commission)

Hope this helps.

You`re working for your money, and getting paid for what you did. It doesn`t sound to me like ribaa, in which you are involved in exchancing something to get increase in its amount. And you`re providing benefit for both parties, so why should there be noreward for your labour? SubHaan Allaah.. If there is cheating or something Haraam being sold, then you`d be doing Haraam by helping it, and not preventing it.
Allaahu a`lam.