Does the iPhone 4 require a SIM card to work?

I want to get off of my contract and change to prepaid but I don't want to buy a SIM card will my iPhone 4 work with out one?

Yep. All iPhones do. They're like in the phone though so it would come with it

You don't have to buy the phone and sim card. Because the iphones you can't open the back of it so it already comes inside of the phone.