The term Professional Photographer had been loosely used to describe an individual in the photography profession.
Lots of points are essential for a professional, but are generally based on,
1) quality/standard,
2) service and ethic,
3) main source of income or solely depended on it for a living, etc.
Class 1 is all of the above,
Class 2 is pt 2 & 3 of the above, ok quality,
Class 3 may only have pt 3, probably ok quality, no exceptional service and ok ethic,
No Class or Low Class, no frill, questionable quality and ethic.
Racehorses are categorized into divisions and classes, div1 class 1 to Amateur classes.
Some started in the lower div and rose to the top, some started at the top and ended at lower div.
All can run, few winners. Best of the best, no horse run but still have losers.
Day rate ranged from $500 to $50,000, minimum or no screw-up is expected.
Its generally perceived that the higher the price, the better the professionalism, not necessarily true but an expectation.
Money is used as a yardstick to measure or qualify all of the above.