HuskyPup - 5:50 pm on Oct 11, 2010 (gmt 0)
So you now have:
subdomain.example.com and you want to buy the subdomain name and point to:
The easiest way would be to url forward subdomain.example.com and point it at newexample.com
Ensure you keep precisely the same directory structure and naming conventions. You may lose rankings whilst Google sorts it out however it should come back within a few weeks and do not forget to delete the old site.
Also, would google see the new site as duplicate content?
No because it won't be there.
Before you do this do ensure you have access to your domain control panel and can perform a url forward with a permanent 301 redirect. This may be free or cost you a few Dollars a year. Your current host may have to set the forwardng if you do not have access.