Study math... Wat do then?

So, i need to apply for college next year. I would really prefer maths (other possibilities would be computer science, physics or engineering), but then i was like 'umm how do mathematicians earn monies?' And how much?
Please, enlighten me.

In my experience, a pure mathematician teaches or publishes books (or the same book as last year but with new pages or diagrams).

You'll probably want to look into what "applied mathematics" means.