Buying an iphone off someone for $200 or getting the same one at the store for.99 cents?

I still don't understand what the differences is. Don't you still have the same monthly payment? I kind of understand the not wanting a contract but if your gonna have the phone for a couple years why buy it off of someone else. Who plans to have a phone for just a few months?
Iphone 4 at AT&T - .99 cents
Iphone 4 off Craigslist/Facebook - $200

You're missing the point. If you buy the used phone for $200, that's not the end of what you have to spend - you still have to get a data/voice plan to use it. Might as well get a new one for 99 cents and sign up for the same plan.

Big difference.

Big differences. A lot (not all) used phones are locked to operate on one certain carrier and a whole lot of them are reported lost/stolen. That's why you never ever buy one from Craigslist because most trolling thieves live there. Unless a person knows what they are doing and knows what to look for it's best they stick with the.99 cents and the 24 payments instead of dealing with the unknown. Also some people have had a phone stolen or broken and need to buy a used on to replace it and can't afford the brand new $659 out-of-the box price that a iPhone 5s replacement costs. Bottom line, they wouldn't be selling them if somebody wasn't buying them. Best luck.