One condition of approval for F-1 nonimmigrant status is that a student shows the ability to pay for his/her education and support while in the United States. The severe economic hardship employment authorization benefit is intended to address situations where a financial need beyond the student's control arises, which was unforeseen at the time the student applied to the school he/she is currently attending and after all other potential employment opportunities have proven to be insufficient.
Examples of unforeseen economic hardship include "loss of financial aid or on-campus aid or on-campus employment without fault on the part of the student, substantial fluctuations in the value of currency or exchange rate, inordinate increases in tuition and/or living costs, unexpected changes in tech financial condition of the student's source of support, medical bills, or other substantial and unexpected expenses."
The student cannot begin employment until he/she receives the EAD card from USCIS.
Economic Hardship Information Guide