Question about a clean install later.

Greetings guys.

I have a question, sorry if it have been answered but I did not find anything my self.

If I buy this offer with the Windows 8 PRO upgrade for the awesome price. I will do a install right away after i bought it.
But will i be able to do a clean install of my computer a year from now?
A friend told me that if I am on Windows 7 like i am now and upgrade, if I want to do a new clean install of my computer a year from now i have to install Windows 7 and then upgrade that to Windows 8 pro since i had bought true the special upgrade offer.
Is this true or is he way out there in the crazy land?

Thanks.

Once you have upgraded, You can not use or sold the old OS.
You can reinstall in say year's time.
http://www.eightforums.com/tutorials/2299-clean-install-windows-8-a.html

So then In 6 months if I want to reformat my computer and do a clean install of Win 8. Do I have to install my old Win 7 and then upgrade to 8, or can I directly install Win 8 with the upgrade version?