Pay to blog/post custom type

I am wondering how to setup the following:

a new subscriber will pay an annual subscription fee (paypal) he/she will then be allowed to create ONE post. This post is a custom type created by the admin (this way the admin controls, the content and layout)

the subscriber can then edit later his post if needed.

SO I am wondering how to setup the payment and the restrictions. Which plugin is best and how would I do it. I have been toying around with s2member but I find it very complicated, anybody any suggestions?

thanks