I did this last year for a 2nd hand iPhone 5 that is still going very well. We arranged to meet half-way (ish) between out homes and we did the deal in about 20 minutes. If you have had other phones, don't forget you need a nano SIM for an iPhone not a regular SIM card. The iPhone I bought was purchased SIM free from new and was simple to de-personalise, wipe clean and fire up on my network with my nano SIM installed.