I've always bought new devices so I've never really had to deal with any used iPhone woes or cautions. I don't wanna get the iPhone 6 this time around so I'm thinking about getting the 5s instead. However I'm thinking maybe i should get a used one and save a couple hundred bucks. Since I've never bought a used iPhone before I'm wondering, besides carrier unlocks, do i need to watch out for anything else? Specifically, is there any possibility of any sort of malware on the used device? Any advice would be much appreciated. Thanks!