Yes, that's a nice article, but again: the computer needs to be compatible with internet recovery. And we are still dealing with some that are not. Additionally, even though it may boot into recovery, it would be unable to download the original OS version - why? Because any OS prior to Lion was never available online, so it can't be downloaded. And that is important because, according to the software licensing agreement, you must wipe anything downloaded from the app store because the license is tied to your Apple ID and NOT transferable. After that, you are supposed to install the original OS which, in such a case, is only available on the originally supplied disks.
So, unless the OP has given specific info regarding the Mac, one needs to consider all possibilities.
Here is a link to the licensing agreement:
http://images.apple.com/legal/sla/docs/macOS1012.pdf
(the transfer rules begin on page 5)