At&t locked iphone 4, 45 and 5?

Where can i get locked iphone 4, 4s and 5. Which r used r new in codition, where can i get this phone for cheep rates so that i can earn some money. I want to earn money of 20k. In which i was cheated buy another person and lost of 80, 000.so please tell me where can i get at&t locked phone so that i can unlock and can sell for better price. In the mean i can earn some money. Please tell me please. Its my humble resquirst to every one thanq

There are many unlock providers on the net or you can do a jailbreak and use a software unlock