I am in USA on L2 visa and I intend to start interviewing/ working immediately. For the EAD application, do I have to apply it before I interview or does the employer apply on my behalf once they make an offer? What are the processing times for EAD? I still haven't got my SSN but have scheduled the appointment for SSN. Should I apply for EAD after the SSN is approved or soon after SSN application?
You should apply (not the employer) for the EAD ASAP. Processing times are on USCIS web site.