If it is a "trusted" site, I would say you won't really need to watch out for anything. Your best bet however, would be getting a firmware version 1.1.1 iPhone and unlocking it yourself. You'll pay less for it in the long run and the unlock (AnySim, which works beautifully btw) costs $0.00 ($0.00 CND🙂) Check eBay for deals on them, however, 1.1.1 iPhones are going for a bit more than you'd pay in stores. If I were you, this is what I'd do.