Building affiliate program link to track

My business is selling products on our website (Wordpress based) and we are trying to set up an affiliate program so people can get paid for promoting our products when someone purchases one of them.

My questions is how could I set up a URL link (http://ift.tt/19ABsqd) and be able to not only track it but see when that person has paid with PayPal so we can pay the proper affiliate

People have suggested clickbank and jvzoo but we would like to do this on our own

Any help would be much appreciated