Mathnasium is an excellent place for people who have a good background in math and a desire to help students learn math.
Pros
Mathnasium is a great place to gain exposure to teaching math to a wide range of students without the intimidation of being in an actual classroom. You have the opportunity to build coaching skills and develop concise explanations for mathematical concepts. The environment is kept focused yet fun. As such, there is always music going on in the background as a room of students work on their math.
Cons
The hours are really flexible, but the center is only open 4.5 hours a day, four days a week. Honestly the most stressful thing for me is when the center is full and you are working with students who are distracting others or refusing to do their work. There are ways to handle this that I'm not proficient at yet, but the center director and other instructors are there to help you with these situations.