If a seller doesn't describe the device they're selling as having a clean ESN, you probably shouldn't buy it. A clean ESN is generally an indicator of two things:
· that the phone is not marked as lost or stolen
· that the phone is not attached to an account with an outstanding balance
Bad ESNs will stop you from being able to BYOMD your phone at all as the system will immediately reject that ESN.
When you get your phone, double-check to make sure that the ESN on the device matches the one you were previously given. If you've already purchased a
device and now realize that it's got a bad ESN, then you should try to get the seller to give you a refund, depending on the terms of the sale.