Great expensive gear - No. A fixed studio open to the public - No. Being " Published " in major magazines - No. Traveled worldwide taking snapshots - No.
Understand people - Yes. Being able to see the image in your mind before you snap the shutter - Yes. Making images that the everyday person can say wow to - Yes.
What defines you as a professional ? When others enjoy your images enough to compensate you, and refer you to friends or business entities.
When do you know your successful ? When you have done enough work that results in a steady enough stream of income that allows you to put a roof over your head, food on the plate, cover operating expenses, and sack a little away for the future.
How does the world know your successful ? When your images can change the lives of others. When your images bring a smile, and find a warm place in the hearts of others.
My secret to success : Give back more than you take and your plate will always be full !