I've been thinking about buying an iphone off a friend...he says, 'I did use it to see how it works and check email at home like right now. Warranty still in tact and still able to purchase APP for it as well. I will click restore from iTunes before buying, so that it will prompt you to activate it like brand new though.' So is this true? Can I just restore it and open a new line, and do all the things I need to do to get it running? Thanks!