I am going to place a PayPal option on my website (the standard account) where the buyer can only buy one item at a time after the price (shipping, etc.) has been decided. I am aware of PayPal's fees, but do the credit card companies also charge me a fee for accepting payment? If so, approximately how much are credit card company fees? I want to use PayPal's email billing option so that the buyer can choose his method of payment.

No they do not charge you. They charge paypal. Look at it this way. Your customer is actually paying PayPal and PayPal gives you a credit in your account. PayPal is the one accepting the credit cards not you. Excuse me if that sounded confusing!