What Vod says is true. Read this: http://answers.microsoft.com/en-us/windows/forum/windows_7-windows_install/selling-product-key-from-msdntechnet-and-or/cf40c328-67ce-49b6-bbb6-c28cda92c06e?auth=1
It is considered piracy and can get your account banned. Also, chances are someone will eventually report you, making all keys void.