A used iPhone is usually a good buy. The risk is not that you overpay by a little — it is that you buy a phone that stops working for you the moment the seller is gone.
There are four ways that happens, and all four are checkable in about five minutes. Do them in this order, because each one can end the deal on its own.
1. Activation Lock — check this first, before anything else
This is the one that turns a phone into a paperweight.
If the previous owner did not sign out of iCloud, the phone stays locked to their Apple Account. A factory reset does not clear it. No shop can remove it. Apple will not remove it for you. The phone is theirs forever, whatever you paid.
How to check: ask the seller to erase the phone in front of you — Settings → General → Transfer or Reset iPhone → Erase All Content and Settings — and then watch it start up. If it reaches the "Hello" setup screen and lets you choose a language and continue, it is clean. If it asks for someone else's Apple Account, walk away.
If the seller will not erase it in front of you, that is your answer. There is no innocent reason to refuse.
2. Battery health
Settings → Battery → Battery Health & Charging shows Maximum Capacity as a percentage.
- 90%+ — effectively fine
- 85–89% — noticeable but usable; worth a discount
- Below 80% — you will be charging it twice a day, and a replacement battery is a real cost you should subtract from the price
Also look for a message saying the battery has been serviced or that the part cannot be verified. That is not automatically bad, but it means a non-original part, and it should be reflected in the price.
3. IMEI — is it the phone they say it is, and is it stolen?
Dial *#06#. Compare the number that appears against Settings → General →
About, and against the number printed on the SIM tray or the back of the box if
there is one. They must match. If they do not, the phone has been rebuilt from
parts or the box is not its box.
Then check the IMEI against a lookup service to confirm the model, storage and warranty status match what you have been told. This is also the number you would give the police if it later turns out to be stolen, so photograph it.
A phone reported stolen can be blocked by the network. You would be left with nothing and no recourse.
4. The physical checks nobody bothers with
Five minutes, in the open, before money moves:
- Screen. Open a plain white image full screen, then a black one. Dead pixels, discolouration and burn-in only show against flat colour.
- Touch. Drag a finger slowly across the whole screen in a spiral. Dead zones are common on replaced screens.
- Cameras. Front and back, photo and video. Check the ultra-wide too if the model has one — it is the lens people forget and the one that is often faulty.
- Charging port. Plug it in. Wiggle it gently. It should stay connected.
- Speakers and microphone. Play something, then record a voice memo and play it back. Make an actual call.
- Face ID or Touch ID. Set it up with your own face or finger. If it fails, the sensor has been replaced and it will never work.
- Water damage. Look into the SIM tray slot with a torch — a red indicator means water got in.
What a fair price looks like
Search the same model, same storage, and look at several listings rather than one. Then subtract for what you found: battery below 85%, a replaced screen, no box or charger, visible damage.
Be suspicious of a price far below everything else. In practice it usually means one of three things: Activation Lock, a stolen device, or a fault the seller knows about and you have not found yet.
Questions worth asking, and the answers to distrust
"Do you have the original receipt or box?" Not essential, but it tells you something about how the phone has been kept.
"Why are you selling it?" You are not checking the reason. You are checking whether there is one.
"Can we meet at [a busy public place] in daylight?" A seller who insists on somewhere quiet, or on evening, is telling you something. Believe them.
The short version
Erase it in front of you and watch it boot. Check battery health. Match the IMEI. Test the screen, cameras, port, speakers and Face ID. Pay only when all of that is done.
Most of this comes down to buying from someone who is willing to be checked.
If you would rather browse in one place than across a dozen WhatsApp groups, RAY Markets lists phones from sellers across Rwanda, with location and seller shown up front.