What would be required to become a therapist?

Depends on the state's licensing requirements or certification requirements for the place you want to practice. There are many different types of "therapists". In some states, any shiester can call him/herself a therapist and hang out a shingle. But if you want to work in a reputable setting or expect to get referrals from professionals, you'll need to comply with the regulations and licensing requirements. These often require four years of college plus a Master's degree or better. The government website for each state should have licensing/certification requirements for different professions.

What kind of therapist are you thinking of? A massage therapist? Do you mean a psychotherapist? A psychological counselor? A Physical Therapist? See if you can be a little more specific.

Colleges have many different diploma programs for family counselling, marital therapy, etc. The program is different on the college you choose but you get about the same diploma for any one. If you go to a university, you can get a degree in marriage and family therapy or social work. It takes 3-4 years usually (minimum) and it usually requires a better high school average to get into than the college diploma programs. Look up some colleges and universities you are interested in. They should all have some sort of social work or family therapy diploma or degree. Usually the only prerequisite from high school to get into these programs is taking all the required courses to graduate high school (they don't require certain math or science or social studies courses).