A career in photography can be conducted on multiple levels. Many professional photographers work for organisations but also work for themselves and often do additional creative and commercial projects as well. This is another 'portfolio career' in which business skills and creativity are the primary elements of success.
Photographic skills can be learned without formal training. However, all media industries prefer those people with formal qualifications and training. The reason for this is that the photographic materials must be used in a very wide range of different types of media, often across multiple platforms. Source photographic materials invariably need to be adapted to the media using them, so the more production skills, a photographer has, the better.
Photographers usually start their careers at graduate level working for media companies. Generally speaking, the early work escalates in degrees of complexity until they have good all-round skills. This training is also particularly valuable in that photographers learn the market for their work. Commercial skills are particularly important for professional photographers, because income streams need to be managed very well in order to have a successful career.
Best practice for professional photographers is to create multiple streams of income. Photography is a particularly portable skill, and highly talented photographers can work with multiple clients.
At this point it needs to be pointed out that there are also multiple possible pitfalls in professional photography. Bad commercial decisions, wasting time on low paying work, and the ridiculous paparazzi mode of 'photography' in which the occasional photo may or may not sell for a few dollars at the expense of other better paying jobs are typical hazards. (Successful commercial photographers won't touch those jobs with a barge pole.)
Photography is a business. One of the worst possible mistakes in professional photography is to conduct business on a 'hobby' basis. Income is too erratic, and business opportunities may only exist for very brief periods of time. Professional photographers must be able to hit the ground running, and provide good quality material at short notice, particularly in the news media.
This is a short list of the characteristics required be to be a successful photographer:
Only the very best professional photographers have all these skills. Photography can be an incredible career, quite unlike almost any other media career, but skills and talent decide career progression. If you're looking for a true challenge, this is it.