Based on a person’s immigration status, he or she may be eligible to obtain employment authorization from the Department of Homeland Security.  A “work permit” can vary in the length of time it is valid.    The underlying basis for work authorization determines the expiration date.  Once a person obtains a work permit, he or she may also request a social security number from the Social Security Administration.  A social security number is given to a person for life, and each person should maintain the same number throughout the immigration process.