eBay is the primary source for used iPhone 4 units. Search for "iPhone 4 GSM" for better carrier compatibility.
The App Store for iOS 7 (the final version of iOS for the iPhone 4) is effectively dead. Installing apps requires advanced, unofficial methods (jailbreaking). i phone 4 buy
Apps like WhatsApp, YouTube, Instagram, and Spotify will not function. eBay is the primary source for used iPhone 4 units