selling mac book pro - HELP

Hi! I recently bought a new mac and i want to sell my own one which originally came with Lion. I have already transferred my files, all that is left is to restore it back to the original virgin environment and let the new owner defile the computer :P

Anywho, I found this article online:

Great, just what i need! Erased the hdd, went back only to see that the mavericks has replaced my lion recovery thingy (I was expecting to see Lion installation, it was Mavericks). I thought - even better! Sell it with the newest software installed!

However, it asks me to enter my apple id in order to install the OS, which makes no sense!!! I want to clean install everything, bring it back to the original state.

Any help? Can I reinstall the system without Apple ID? All I want is to sell the Mac and when the new owner gets it and opens the screen to see the Welcome, choose a language, insert your apple id thing. HELP!