I believe a good portion of them usually seek additional hours, whether it be via additional TA roles, additional marking roles outside of the program or additional research hours. I cannot think of any students I know of in a master's or Ph.D. role right now who do not either work with a company through their Ph.D. to increase their overall funding or who have not sought additional working hours from their professor. I think that tends to be the most common role.
I grew up working in the restaurant industry alongside school, so that was an easy option for me to have alongside my research career. However, most or all of the graduate students I know tend to seek additional work hours in some form or another.