PayPal or some other PayPal-like system is the way to go for what you're describing.
To do full blown credit card processing, you'll have to get a merchant account. Then write some code to interface with a payment gateway. Plus you would need SSL to securely handle the credit card numbers between web pages.
Check with some banks, but I think you'll find there's a setup fee, transaction fees, monthly fees, SSL fees (yearly), and the gateway may have fees as well.