I was going to go with PayPal for recurring billing because they have a powerful API and are relatively low cost. But after reading this The PayPal Fiasco I decided this was a very bad idea. PayPal could shut me down anytime they wanted, for any or no reason, and keep all my money. I would be basing my entire business on the mercy of a third party that doesn’t care about the success or failure of my business and in fact has self-interest to see that I fail. My alternatives are a lot of trouble but so far the best seems to be Payment Online. For some upfront fees they have the lowest rate of 30 cents plus 2.15% per transaction. The company looks professional and they offer APIs that seem to do everything I want.