You are selling illegal Microsoft keys.
The Microsoft Developer Network (MSDN) is a set of online and offline services designed to help developers write applications using Microsoft products and technologies. MSDN Subscriptions are available at three levels. This offers developers, teams, and organizations a choice in what is included in the subscription.
You are not using your MSDN subscription for developing and you are selling the keys for profit.
These keys will no longer work when the MSDN subscription gets blacklisted/removed.Only the account holder of an MSDN subscription is supposed to be using the licenses, and only for software development/testing purposes.
These keys are not to be sold, at all, ever, for any reason.
Here is what the makers of the MSDN subscription say:
https://msdn.microsoft.com/subscriptions/cc150618.aspxThey even modified their terms to specifically try and stop people like yourself:
https://msdn.microsoft.com/en-us/subscriptions/cc137104.aspxIs it too hard for you to find a legitimate business practice to make money?
If you really want to resell keys, hope this is helpful:
https://mspartner.microsoft.com/en/us/pages/licensing/become-a-licensing-reseller.aspx