Some agency of webhosting, allow automatic credit card payment every year without entering each time the credit card number and CCV code.
How could I do this ( asking user's permission of course ) ?
There are several companies that can provide you with recurring billing capabilities, which will not only take the development workload off your plate, but handle the PCI requirements. Take a look at Recurly, Chargify, Cheddargetter, or Spreedly. Based on your needs, one of these companies should be able to help you out.
Disclaimer: I work for Recurly. I'd be happy to answer any of your questions or point you to the right processor for your needs.