Not all secondhand phones are equal, many phones that are sold to a shop that specializes in secondhand phones will be cleaned down, inspected and have the OS reset. Damaged phones may get repaired, giving the user a like-new refurbished phone.

Private sellers or less reputable shops may not be so rigorous with their testing and clean up. Quite often the phone will be sold in a worse state than advertised. Private sellers in particular, may forget to do a factory reset of the phone. Worst case scenario you may find the phone is completely blocked or another major feature not working.

Even well a phone is sold in good condition; another concern is how old it is and how likely the company will keep updating that phone.

Some secondhand phones may be stolen

The worst-case scenario is that the phone may be stolen. Assuming you have not deliberately bought a stolen phone, the main concern you have is that when it is reported stolen then IMEI number will get blocked, rendering it almost useless, as you wont be able to make calls or receive data.

Therefore it is paramount to ensure that you buy your phone from trusted retailers who offer appropriate documentation for the gadget's possession.

For online purchases, you should try to use PayPal or a credit card when buying a phone, both these methods offer buyer protection, so if a seller does sell you a stolen phone you can get your money back direct from PayPal.

Does it contain viruses

All phones should be fully reset when you get them. So when you switch on the phone, you go through the basic set up procedure again. As someone that reviews phones for a living, it is not uncommon for a PR company to send out a phone pre-set up for you, this also happens when you buy phones from China, I ALWAYS reset the phone, you just don't know if or what additional software has been installed.

To be extra careful, when set up you can go into the phone settings and double-check it is using the correct OS for that device (its possible to flash some phones with different ROMs).

Phone security updates

The above issues should not happen very often and are easily mitigated. However, buying a secondhand phone means you are likely buying something that is months if not years old. Phone companies only update the OS for a limit period of time; some brands are better than others.

As much as I dislike iPhones personally, these are the best for OS updates receiving several years of updates, so they are always a good secondhand purchase and one of the reasons why they retain their price so well.

Google and their Pixel phones are a safe bet too, and most brands making Android phones offer two major updates.

It is best to try and Google to see how long a company will offer security updates for. For example, Samsung provides monthly security updates to its flagship phones for up to three years, after which they usually stop receiving security updates. However, they have been known to extend this, issues quarterly updates instead.

Many people continue to happily use a phone after security updates are stopped being received, and the chances of something bad happening are minimal, but the longer you leave it the more insecure it will become.

Get the right price

Although different sellers offer different prices, most of the costs are determined by demand and supply forces. However, you may be tempted to go for the cheapest, which may be expensive in the long run. Before undertaking a purchase, conduct thorough research on the best deals and the authenticity of the product. A comprehensive analysis ensures that you get the right secondhand phone at the right price. Moreover, it helps in identifying the best sellers by reading past reviews of buyers. After adequate research, plan your resources to determine the amount of money you need for the secondhand phone. Ensure that you visit the store to check whether the phone is in the right condition, whether it contains all the accessories, the buttons are in good condition, etc. Ask for a warranty; professional sellers offer a guarantee of one year for gadgets such as phone.

Then for online purchases, don't forget to use a payment method with buy protection (PayPal or Credit Card)