Graduate programs require you to teach, usually an intro physics lab - which I did. The pay was decent for a graduate student living off campus, but there was some extra time that had to be allotted to the lab. Instructors were required to lecture about the lab topic (most of the course lectures and labs do not align and they can be doing a lab over a topic they have not seen yet, or saw weeks prior and forgot), quizzes about the lab, which had to be solved and graded by the lab instructor, and a final exam that pertained to all experiments over the semester - this exam was 50 questions, multiple choice. There was no answer sheet for the exam, so the instructor needed to take time to go back over all past lab handouts and find the answers to the specific steps/procedure of the lab. Of course, that is the work of a professor, but time management was the most important aspect, since you are taking 3 graduate level courses as well.