SOURCES:[1] apple.com[2] macrumors.com[3] backmarket.com[4] gazelle.com[5] swappa.com[6] nytimes.com
Confirm the phone is "unlocked" so it works with your specific carrier.
Next, he discovered like Back Market and Gazelle . These sites are like high-end thrift stores for tech; they professionally inspect and grade every phone (from "Fair" to "Excellent") and offer their own warranties [3, 4]. This felt like a great middle ground for quality and price.