Does iphone need wifi to work?

my friend wants to sell me his iphone 3g he no longer uses but he said it doesnt have wifi. i was wondering if wifi is needed in order to be able to use the phone. im only goin to be using the phone to make calls and text and for the music. anybody help please. o and can it be use with a pre paid plan i might give it to my sister but shes on pre paid.