I plan to always have a church job to support me, and as a relatively experienced organist, and the fact that there is ALWAYS a shortage of organists, I am pretty much guaranteed to have a steady organ job all my life.
That's what you have to do - find your steady back-up job. Most composers (after getting countless degrees, mind you) teach at a university level. Usually they teach theory, counterpoint, orchestration, or some just do composition lessons and masterclasses. But I don't plan to teach, so the organ thing is pretty much my only choice.
Once you find a way to have a steady income like a church job, freelance jobs, a position in an orchestra (good for you instrumentalists), etc., you can live AND compose at the same time!
Of course, marrying someone who has money or is willing to support you and your passion would always help.
