A Vendor is an independent contractor.
....so you're responsible for your own insurance and health care.
Microsoft doesn't sell software Partners do.
Independent Software Vendors build on the Microsoft stack - Windows Vista, Office, Windows Server, SQL Server, Exchange Server and sell their software into Verticals - Health care industry, Manufacturing, Government, Education and many more.
I was talking on the phone last week to the guy who runs the Partner ISV program at Microsoft and he's going to be in Beijing this week.