What do I need to become a tutor?

Money is tight right now and I’ve had several people tell me I should try tutoring students. I suppose I have a tendency to “teach” people and generally have an affinity toward children. I’m also patient to a fault. The problem is, I’m feeling unsure of myself.

Background info: I did very well academically throughout school (including high school math, though I hardly remember it now). In college, I majored in English Lit and minored in Philosophy, and got very good grades.

Do I need to be certified to be a tutor? What does tutoring entail exactly? It can’t just be homework help; I probably need to have my own materials to supplement whatever I am helping the student with. Where do I get these materials? Is it a big investment? (reminder: money is tight)

There’s a part of me that just feels wrong about taking money from people for a service that I do not know the efficacy of. I’ve helped my younger cousins with their schoolwork on occasion, but I have no way of knowing if my help, on a consistent basis, can improve a student’s grades. Isn’t it somehow unethical to take money from people without knowing if my work will help their child?

Another concern for me is that I don’t know the kind of work that a child should be doing at each grade level. If I see an essay written by a 6th grader or a 9th grader, I’m sure I’ll be thinking about them the way I would a college paper. How does one learn what can be expected from a child of a specific education level (without actually going to school and getting a teaching degree)?

How do I figure out what to teach? It seems to me that science, social studies, English and math up until algebra are easy enough to help someone with. Or are they?

Advice from experienced teachers/tutors is especially welcome.