It depends on what is meant by becoming an astrologer.
In the first instance, the passion for the subject, a smattering of the symbolism of signs, planets, aspects, and in a few months, you can show off your knowledge with friends and maybe try your hand at some prediction based on zodiac signs. This phase can give rise to some misunderstanding, especially for the not insiders (sceptics), who tend to identify astrology with newspaper horoscopes.
Then we have the stage of the astrology courses. If they are well managed, they provide proper basic knowledge of the fundamentals of astrology: birth chart and its interpretation, basic forecasting techniques such as transits, solar revolutions, progressions, etc.
If you continue, things get complicated. I am not talking about the need to study advanced computational bases because there are many ad hoc programs nowadays. Still, at a certain point, it turns out that there are many astrology addresses, which use very different techniques that it is necessary to know. Moreover, one becomes aware that astrological symbolism is much more complex than expected. It is a university-type study requiring an interdisciplinary astrological culture (including history, mythology, philosophy, psychology, alchemy, and science).
Finally, it turns out that the training never ends. It is the moment in which, if one assimilates the studies on the subject, astrology becomes an individual path, preparing for union with the inner sky. Here begins the most challenging phase, but also the most rewarding one, or as Ptolemy, famous astrologer and mathematician of the second century, said:
I know that, as a mortal, for only one day I was born, but if I follow the dense multitude of the stars in their circular motion, my feet do not touch the ground, and I go up to Zeus, nourisher of gods, for satiate myself with ambrosia.