How much is the Iphone 3g monthly fee?

My friend is selling her Iphone 3g to me for 100 dollars, and she has at&t and so do I. I don't know how much the monthly fee is. I think it is 30 bucks but i don't know… I really don't want to pay that… Help!

That depends on the plan options you take & how you use it within the month. You should contact AT&T concerning that & see what they say.