There are PCI compliant ways of storing this data, and even better there are companies you can pay to do it for you (so you don't screw it up) while providing a

There are PCI compliant ways of storing this data, and even better there are companies you can pay to do it for you (so you don't screw it up) while providing a lot of other goodies at the same time. See: Braintree, and Stripe.