It's possible to enter DFU mode and restore via iTunes however that only removes the passcode lock, it won't remove the iCloud account is attached to it.
More than likely, the iPad is stolen so I would avoid it. You could find out by contacting the seller and telling them to DFU restore and then remove their iCloud account. If they can't do that then it is stolen
Answers & Comments
It's possible to enter DFU mode and restore via iTunes however that only removes the passcode lock, it won't remove the iCloud account is attached to it.
More than likely, the iPad is stolen so I would avoid it. You could find out by contacting the seller and telling them to DFU restore and then remove their iCloud account. If they can't do that then it is stolen