I am on F-1 Visa and applying for Green Card. If my F-1 expires, can I work legally while my green is still in process?

Adjustment of status may be used by someone in F-1 status to become a lawful permanent resident. However, adjustment of status is only available if an immigrant visa is immediately available to you. You cannot file an application for adjustment of status if your priority date or application filing date is not current. In your case, you indicated the process would take about ten years. This indicates that you fall into a presence category and must wait years for a visa to be available. If this is correct, you cannot file for adjustment of status at this time. You could only do so in about ten years when the visa is available. You are not authorized in the United Srates simply because an immigrant visa petition is pending. You also are not entitled to employment authorization. Upon the completion of your studies, you will need to depart the United Stafes or change your status to another nonimmigrant category. You can read more about family immigration at http://myattorneyusa.com/family-immigration.