Can i trust buying an iphone off of craigslist?

I talked to my phone company and they told me that I'm not eligable for an update for like a year and a half. They did happen to mention (because i want the iPhone) that if I got one from a friend or family member or off of a website I could swap phones basically with no extra charge. I want an iPhone so badly and I might be able to get my aunts old one (because she is getting the 5) but if that doesn't work out, would you trust buying an iPhone off of craigslist?

I bought a car off craigslist. Try out what you buy inspect it. Before paying up. Try registering it to your service providers account. If it doesn't work. This person may be selling you a stolen phone. Just make sure your getting what you payed for. Stay safe