As an undergraduate Psychology major, will I have an opportunity to make money before/at grad school?

Yes, you just need to find a grad school that offers teaching fellowships. A teaching fellowship includes assisting a faculty member at your grad school, and sometimes teaching undergraduate courses on the side. When I was working on my Ph.D., I was a teaching fellow at Cornell and I helped my professor with her research, and she helped me get mine published, which paid quite a bit as well. I finished my doctorate last year in Social Psychology with very little debt (only about $3,000 from my grad work). I had debt accumulated from my undergrad as well, but from the research I got published, I got most of that paid off as well. Moreover, by being a teaching fellow, I gained valuable job experience which, I feel, helped me get a professorship when I finished. Overall, I'm paying off about $5,000 in college debt, but I make plenty of money as a professor so that doesn't really matter.

For getting into the mental health field, you may want to consult your graduate advisers and discuss paying for your higher education with him/her. You should also find a psychiatric hospital or something to work at while your complete your grad work. I don't know of any paid internships/fellowships for the mental health field, but you may want to work under a licensed clinical psychologist or something like that. Good luck!

Yes, but not very much. You could work at a psychiatric hospital as a tech, or a group home as staff. You could work as a teachers' assistant in special education. You can work and go to grad school at the same time. There are often fellowships and scholarships available, but loans are usually necessary. I recommend applying for Perkins loans. The Financial Aid Office can help you. Don't be too proud to apply for unemployment or food stamps if you qualify. You may wish you had later.

Contact your College ad visors in your department as well as the research department. They are the people who can give you an idea on how to pay for your education as you go along trying to complete a degree.