Apartofme, you can see from this thread that there are many different opinions: we do not all agree. Here are my views.
Technically speaking, an amateur does not charge for what s/he does. The root word of
amateur is the same as
amore: meaning love. Amateurs and professionals alike can love astrology, but it is the key motivator for amateurs, not income.
Kepler College, in Washington state, appears to be very much open, but not as an accredited college.
http://www.kepler.edu/home/ It offers on-line and classroom courses, workshops, and certificates.
There are several prominent non-profit societies in the US that offer courses and tests, such as the American Federation of Astrologers and the National Center for Geocosmic Research. Astrologers who pass their exams are entitled to put this credential on their promotional materials, such as websites and business cards.
Astrology exams are highly controversial in astrology, but they were established by professionals who were sick and tired of ignorant amateurs giving astrology a black eye. Right now, you, I, or Daffy Duck could call ourselves professional astrologers, as the field is largely unregulated-- unlike other professions.
Also, individual well-known and published astrologers often offer on-line courses and their own diplomas to astrology students. Further, there are programs in Britain that offer on-line programs, some even offering degrees, like the Faculty of Astrological Studies
http://www.astrology.org.uk/ but these are usually not accredited. The one that is, Bath Spa University, actually doesn't teach professional practice, but students can study the history of astrology, or astrology as a cultural practice in society.
There is another recent thread on this, but be advised that in many US states, astrologers cannot use the word "psychology" or "psychological" (as in "psychological astrologer") in their titles, unless they have met the state's criteria for licensing as a clinical or counseling psychologist. This is a very high bar, requiring a Master's or doctoral degree in psychology or closely related field, plus board exams.
I would skip the more woo-woo approaches, if I were you. Most people who pay for an astrologer's services want either a competent personality analysis; or else they have specific questions about their money, relationships, or career.
Oftentimes, you have to know predictive methods to answer their questions, such as horary astrology, or various methods of forecasting.
At one time, I thought Dane Rudhyar was hot stuff, but it is hard to see how you could use his material on the Evolution of Man Through The Signs to advise someone on why her boyfriend left her.
Modern western, traditional western, and Vedic (jyotish) astrology all produce good results in the hands of competent practitioners. If you explore them all, you can see which one feels right to you.
One of the best things you can do now is read as much as you can: but be a connoisseur. Astrology in books and on the Internet contains the good, the bad, and the ugly. Then start reading charts for people. A "live" chart will give you so much more interaction than just looking at one in a book, in my opinion.
Even if you don't know much astrology, you can start with people's sun, moon, and ascendant; and let them know you are still learning.
If you are university- or college-bound, one of the best things you can do is to study a field that teaches you about human nature-- and then become active in volunteer activities that bring you into contact with a wide variety of people and their stories. An introductory course in astronomy would be helpful, as well.
Good luck to you!