How to transfer WoW character to other b-net account?

[egan]

I see some seller just sell a character, not a whole account.
How to do that, can someone explain this?
And how about the Achievement or mount, is stay with old account or transferred to new account?
Thanks.

 

[EpicNPC]

They create a new battlenet account with WoW and transfer the individual character to it. I'm not sure about the achievements and mounts.