Small piece of advice, do not buy Yahoo Publisher Network invites. A member at WebmasterWorld bought an invite and then was denied, since he wanted to sign up under a different URL. Afterwards, he was accepted into the program but now has two different accounts.
Good thing the Yahoo! folks are laid back, it seems like the consolidation of the accounts will go through and everything will be fine for this user.
But it is not recommended to buy invites. I guess they are selling them somewhere on eBay.