.....I always felt this way. There is the professional drummer and there is the career drummer. A professional drummer would be one that gets paid to play the drums, regardless of age, for entertainment purposes. And I feel they have every right to consider themselves as being a "professional". I do. Getting paid for a service rendered is what you are doing, and usually that is considered being professional. Now, a career drummer is the one that can maintain a living by only playing the drums. No full / part time job to help supplement their financial status along with their drum pay. They are most likely a part of the musician's union as well. But I think all of us here who have played clubs, parties, teach, whatever, and that got paid, are all "professionals". But I doubt many of us can actually make enough money to support ourselves, families and life styles by playing drums alone. Those drummers are much more rare. Sometimes it's also being at the right place at the right time, which no one has control over that. Making a career from drumming is not impossible, but it is harder to accomplish. It takes even more dedication but most of all, more risk. So I say ALWAYS have a back up plan just incase.
I think you need to decide just how much risk you are willing to take. There's much competition out there and the industry is non-forgiving. Life is full of risks, but it's up to us to choose wisely.....until you decide however, practice, practice, practice and assume nothing comes easy....