With the release of iOS7 last year, Apple introduced the Activation Lock anti-theft feature. iPhone owners who enable Activation Lock can erase and lock their phone if it is lost or stolen. The Apple ID and password of the owner is required to reactivate the phone... without that, the phone is as useful as a paperweight.
Police departments confirm that this feature has led to great reduction in iPhone and iPad thefts. If buyers of used iPhones are not careful, though, they can become a victim by purchasing a phone that cannot be reactivated. Here's how to protect yourself.
As always, if the offer seems too good to be true, it probably is. Be wary when buying a used phone on sites such as Craigslist.
Ask for the ESN/IMEI of the phone. The seller can find it under Settings > General > About.
Use http://checkesnfree.com to check if the phone has been reported stolen. It can take time for an owner to report a device stolen, but this is a good place to start.
Meet the seller and check the phone before you pay any money. Go to Settings > iCloud > Find My Phone, and make sure it is disabled. Have the seller disable that before paying any money; if they don't know the Apple password required to disable that feature, the phone may be stolen and is not useable.
Go to Settings > General > Reset > Erase All Content and Settings to remove the previous owner's data and start from factory settings.
“Activation Lock” is not your only worry. If the owner has stopped paying their service provider, they will need to pay back payments before you can continue the contract yourself. It’s best to meet at the service provider’s store so that they can change the contract to your name while the seller is still there.
Used iPhones can be a great deal, and, when the iPhone 6 becomes available (this fall, according to rumors), used iPhone 5 and 5s models will become available at discounted prices. By cautious, and you can find a good deal.