Since I'm responding negatively, i would like to point out that I am still in high school, ergo I make a living rolling burritos at a restaurant called Qdoba, and play guitar at friend's parties in exchange for money and occasionally food.
It has never been possible to make a living SOLELY as a composer. Even the greatest either had huge grants from Kings and financial assistance which is impossible to come by today, or they made livings on the side doing other things. Many played piano for a living, and Charles Ives was an insurance Salesman.
People could once do as Charles Ives did. Their respective Jobs generated them enough money to keep their businesses afloat. Unfortunately, in today's music industry, i no longer beleive it is even worth composing music at all. Look at how the music industry works. Everything you hear on the radio or buy in a record store has been run through countless surveys to make sure you like it, and to make sure as many teenagers, the primary consumers of music, will buy it as physically are able to.
They've figured out that orchestral music doesn't sell in that demographic, and as a result, most major label record companies have all but shut down their classical divisions, and if the classical divisions are afloat, they release film music or music by dead guys (more about that later). As a result--music by new composers doesn't get played, the theory being that no one will buy it.
The Music that does get played, is music by dead guys, Mozart, Beethoven, all that filth. This is done for two reasons-- the music is already well known (who hasn't heard the famous "fate" motif of the fifth symphony), the orchestras have been hacking their way through it since their conservatory days, and it's cheap...you see, when you're dead you don't collect money for having your music played. Why would anyone want to finance music that will have to be rehearsed, be promoted (as it is a new peice of music and people dont know about it) and then played (incorrectly), and on top of that pay the composer? Why waste all that money when they can earn far more money far more easily by hacking their way through a couple of classical "standards" or a soundtrack of film music (which is basically all the same these days and thus not difficult for orchestras to play).
I do beleive that good music is out there that is getting composed, i've heard a lot of it on this website. However, when it does somehow manage to get through a record company and get released, it's nearly impossible to find, due to the fact that retailers can make more money by selling records by Korn than records by Steve Reich.
For these reasons I beleive it is not possible to make a living as a composer anymore, unless your in the field of music or videogames. both of these will always need music for it to appeal to the emotional side of people's brains and heighten their respective experiences, so film and game music (most of which is hogwash.) will always be around.
Many of you will be hostile to this...many want to beleive that they can be composers, but I say--FACE THE FACTS. I love composing music and I adore classical music and new music...but if this kind of music is going to survive, SOMETHING MUST CHANGE. the question is what?