If you have a used smartphone or tablet lying around that you’d like to sell, or if you’d like to buy a used device, Connecticut Better Business Bureau says you have many options, but some of them are risky.
“We see a situation in which some websites will quote several hundred dollars for a used smartphone or tablet sight unseen, and then offer a substantially lower price once the consumer sends in the merchandise for evaluation,” said  Connecticut Better Business Bureau Executive Communications Director, Howard Schwartz. “Most of the websites that purchase these electronic devices are reputable, however, there are patterns that emerged several years ago when gold prices were high.”
Similar to smartphones, several years ago, consumers were urged to put their jewelry into a prepaid envelope to receive top dollar for their precious metals.  Unfortunately, there was considerable consumer dissatisfaction with some of those business’ lowball payouts.
There is a big market for used electronic devices, however, some consumers were quoted $100 for a used smart phone, sent it in, and were subsequently told the merchandise was only worth $25. In one complaint to BBB, a consumer told of one site that said his used tablet was worth more than $300. However, once he sent it in, he was told it was only worth $45 because of “current market conditions.”
There are a number of ways to buy and sell used electronics, including specialty websites, online auction and classified ad websites, and social media marketplaces.  Whether you are buying or selling, be careful to only pay with or accept secure methods of payment.
Connecticut BBB has a checklist for consumers looking to buy or unload a used smartphone:
Prepare it — Back up your device’s data such as photos and contacts if you intend to sell it and follow the manufacturer’s instructions for a “factory restore” to wipe clean all data from the device.
Do a thorough check — When you are buying one, ask for photos of the device as well as the phone’s serial number.  Using that information, a number of online databases can tell you whether the phone was stolen.
Make sure the screen, Wi-Fi, data and charger connections work, and see how long the device holds a charge. Battery life predictably shortens with age.
Make sure it is unlocked — A smartphone is often “locked” to a specific wireless carrier if the seller is still under contract. The vendor must provide the phone’s original “SIM” card and get the device unlocked so that you are free to use your own SIM card and service from whatever wireless provider you choose.  An unlocked phone also allows you to use the phone internationally.
Take photos of the device — If you send your smartphone or tablet to an online electronics website, take a set of photographs to document what condition it is in. This may help you in the event the buyer claims the phone was in poor condition.
Be realistic — See what the marketplace is like. Check what other people are asking for the same model of phone, and assume that any quote about the phone’s value is meaningless until it is examined by the buyer.
Consider those who need an emergency phone — Not everyone can afford a smartphone and there are a number of nonprofit organizations that would appreciate such a donation, including schools, city drives and local domestic violence centers. If the device is damaged beyond repair, you can bring it to a recycling center to dispose of the battery and other environmentally-unfriendly materials.
If you are planning to buy a used smartphone, you might get a good deal upon the release of a newer model, when the market is flooded with older units as users grab the latest gadgets.
You can check the reliability of businesses that buy or sell used electronics at bbb.org.