I can only speak of what I know from an undergraduate standpoint. I have many friends who work as desk attendants, in the library, at the information desk, or the admissions office, etc so campus jobs are definitely out there if you actively pursue them. I am not sure if you need to be a US citizen or not for these jobs. I would recommend emailing the department that you will be in and asking them these questions directly since it will very important to find out! Good luck!