We're on ATT and I got my wife a 3GS refurb through ATT and our FAN# for $9 about a year ago. After playing with her 3GS, I realized no matter what beefs I had with the mobile provider smart phone pricing structures, I needed an iPhone. I got a refurb iphone 4 for $99 and absolutely flipping love it; can't believe life existing with out it. Don't much care for the monthly bill, but it is cheaper than a drug addiction. However, now my wife is giving me grief that my cool new gadget is better than her gadget and how come I always get the really cool gadget and she gets the busted down reject. (Mind you, she had an iPhone first and I had no phone.) So I'm looking at used iPhone 4's on Craigslist and need to know what to watch out for. Prices are all over the place, but I think I can get a decent clean 16 to 32GB unit in the low to mid $300's. Does this sound about right? Can I use the SIM from her 3GS in the 4? Do I have to involve ATT any where in the switch? ($$$) Are there any common scams I should be aware of? Any common red flags to watch for? On Edit: Should have done this first. Googled found some good tips. Any extra tips from the masters would be appreciated.