This actually brings up a couple of good points, sorry to go off topic
Many of the threads and sites you see online that mention "start your own processor" are typically referring to clones of paypal. The fact is, paypal is not a payment processor in the traditional sense, they are a third party biller. If anyone is familiar with them, payment processors include FirstData, Global Payments and others. These are companies that actual handle the payment processing itself. Not payment processors are also confused with companies like authorize.net, those are actually payment gateways.
Thought I'd help clear up some confusion because I hear this all the time
One final thing, while there may appear to be many paypal style sites, the reality is that at least in the United States, these sites are in fact many transfer agents and if you are in the United States, you have to be licensed in every state in which you do business in addition to the federal government. It's a very complex process, much more than just buying a $25.00 paypal clone script