While in college, I began training in Gojuryu. In one particular class my sophomore year, we were asked to write a letter to ourselves that the teacher would send us in 10 years. 10 years later my parents forwarded me the letter. One part in particular read, "I don't know what this letter will find you doing, but I know that you are teaching karate somewhere."
When I began kenpo, I told Mr. Finn on my 2nd lesson that I wanted to teach this for a living, and that as soon as he needed an instructor, I was in. He laughed and explained that he heard that alot. 3 months later, I was teaching kenpo.
Then one day one of my students mentioned that he was moving to Louisiana and had enough money to secure financing for me if I would be willing to move to Shreveport and open my own place...
There is no real "when" for when my passion became a profession. It seemed natural. My father always told me that the secret to happiness was to find the one thing you would do all the time for free, and figure out a way to get paid to do it.