Ok, here is my master plan but I don't know if it will work. I have to pay a $200 dollar deposit to ATT for an iphone due to credit reasons and then i can buy a refurbed Iphone 8gb online for 150. My plan is to then sell said cheapo Iphone on ebay for $400 dollars or so and buy a 16gb new iphone at the store. Will this work? I see no problem but im sure I missed something. Thanks!

Um... sure? Why don't you just save for the 16gb iPhone, cause it's gonna cost btwn $20 & $40 per month...