Check out
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to check your ESN's, etc.

As for selling the phones of course that is different, if it's blacklisted lost or stolen you're screwed, but if it's just a unpaid bal sell the phone as parts. Locally if I get a phone that is reported stolen I am required by law to surrender it to my local law enforcement. I copy the ID of each person I buy a phone from along with that they sign a sales agreement that they are the legal owner, just like a pawn shop.

If by chance I do need to turn one in, I get a receipt from law enforcement stating the reason why and the market value of the item so I can claim it as a loss on taxes.