How does Amazon Trade-In work?

I have an iPhone 3GS I'm selling for $70. I'm wondering how long it'll take until I receive the money. Will it be deposited into my banking account after they approve the item, or once they actually ship the phone to someone else?

You'll get Amazon gift card credit when they approve the trade-in. So you'll need to buy something else from Amazon to get your phone's value out of the program.