Smartphones have become an important part of our lives in today's fast-paced digital world. But it can be pricey to buy a brand-new smartphone. A lot of people who want to save money choose certified pre-owned (CPO) phones, these gadgets have all the features of a new phone but cost a lot less. But you need to think carefully to make sure you're getting a real, certified pre-owned phone. Here is a complete guide to help you buy something smart.