No, sponsoring him neither produces a contract of employment (implied or otherwise) nor offers him job protection in the event of a layoff. He gets treated exactly the same as any other employee; he cannot be discriminated against but he gets no special privileges. Someone else doesn't have to lose their job because he's got a work visa and is applying for a green card. You take the visa completely out of the equation and make your decisions without that factor (BTDT).

