Buying iPhone 5/ 4s in the US and using it in the middle east?

I have a friend who's flying to US for a short while and wanted to get an iphone 4s/5 down from there as it is much cheaper than buying it from where I live in the middle east. I know I'll need one that's factory unlocked, but would there be any other factors against bringing an iphone in from the US? Also what would be the best place to get one (no contract) in the US?

You can purchase an unlocked iPhone directly from Apple. Of course it is going to cost an arm and a leg to get it unlocked though. It might even be cheaper to purchase the phone from a carrier, then pay the early termination fee. If you did go that route (assuming it is cheaper) than you will need to jailbreak the phone and then unlock the sim to use it with a different carrier.