Question:
I have not filed the I-485 application yet, but I need to apply for the Work Permit for my wife. How do I get employment authorization for her as soon as possible.
Answer:
To get the work permit or employment authorization, the Form I-765, Application for Employment Authorization, should be filed with the United States Citizenship and Immigration Services (USCIS).
Generally, the employment authorization application should be filed together with Form I-485 application for adjustment of status simultaneously, without paying the Form I-765 application fee.
But if the employment authorization Form I-765 is filed separately with the Form I-485 application, an Form I-765 application fee should be paid to USCIS.
http://www.greencardapply.com/question/question14/Work-Permit-Application_0310.htm