How much is a used iphone 3 worth for?

My friend is selling her iphone 3g i have tmobile, its unlocked and everything, if i get it will there be any problems? (: thankss in advance! :

No there should be no problems. The only thing to consider would be that t-mobile does not support 3G data on iphones so you will only have the slower EDGE internet.

I have an unlocked iPhone 3perfect condition. Trying to sell. 916 968 2949