Many cart have recurring billing except that they are NOT PCI compliant!
No-one that is doing recurring billing can really be PCI compliant because in order to do recurring billing you have to keep credit card in your database (Yikes!)
This is really bad.
If you need to protect content, then anelegant recurring billing solution that is also PCI compliant would be to use wordpress with one of those latest plugin that charges automatically the customer without having you to keep the customer credit card.
You pay the plugin monthly fe and they protect you by managing the credit card info and also managing the access to the content.
If you're interested I will give you the name of that plugin, I just have to look for it on files.