Is it having a good eye? No
Is it having a good camera? No.
Is it having excellent skills? No again.
While all of the above are helpful, what makes a photographer a professional is their attitude toward their work.
A photographer who treats photography as a vocation, and not as an avocation, is a professional.
When your attitude shifts so you view photography as your business and not as your hobby you’ll become a professional.
You’ll learn to price your work, you’ll learn to market yourself and you’ll begin to make money doing something that you love to do.
Don’t think of going into photography as a business because you want to do what you love to do.
Go into photography as a business because you want to make money. Getting what you love to do is a perk. It’s a HUGE perk, but it shouldn’t be the primary reason that you get into the business of photography.