Hundreds of thousands of artists and bands want the answer to that question.
With hundreds of thousands of bands and artists all trying to be rich and famous.... chances are really good that more than 99.99% won't be....rich or famous.
It's possible to place music into libraries and with publishers but again that is not as easy as it used to be either. Nobody wants demo quality stuff anymore. It all has to be record ready and broadcast quality. With all the home studios and the tools we have, the music has gotten better and the bar has gotten higher. Much higher.
A few years back, at a songwriter's convention, in a country music session talking about pitching to Nashville..... I had the opportunity to hear the "demo" submitted to a recent #1 hit song bu a country super star group. They played the "demo" first and the quality of the demo was so good it could easily have been released on it's own.... the only difference was the intro guitar lick was slightly different and the singer's voice was slightly different from what we were used to hearing on the radio.... it could easily have passed as the radio single by the big artist.... the demo was that good.
Sell on CD Baby and other sites.... but the key to sales there is promotion. That costs dearly. Gig with your band and sell in the clubs. That's the most reliable way to sell your music to the fans.
Good luck.