In the era of patronage, when most artists were funded by the church or the nobility, often in competition with one another, what you had to do was fairly clear, I would imagine: appeal to the tastes or vanity or ambition of your patron. Italy seems to have been particularly blessed with wealthy, visionary patrons which partly explains the great art of the Renaissance and Baroque. As the eighteenth century came to an end the patronage began to shift from the aristocracy, more and more eliminated by revolution and social change, to a widespread support by the middle class, who began to adopt some of the artistic tastes of the nobility. Haydn was supported for most of his life by a single aristocratic family, the Esterházys, Beethoven by a circle of wealthy patrons, but Schumann wrote music criticism and edited a journal. Chopin taught private students, Mendelssohn was a conductor, as was Mahler, and director of an important music school. Some composers, like Wagner, still had aristocratic patronage, but that was rare in the later 19th century. By the time we get to someone like Sibelius (1865 - 1957) the struggle to support a family was dire indeed. Here is a lament he wrote in 1911:
My domestic harmony and peace are at an end because I cannot earn sufficient income to supply all that is needed. A constant battle with tears and misery at home. A hell! I feel completely unworthy in my own home ... Poor Aino! [his wife] It can hardly be easy to manage the house on so little. It makes me more than aware of the truth in the old saying: do not marry if you cannot provide for your wife in the style to which she was accustomed before. The same food, clothes, servants -- in a word the same income.Sibelius, like many Finns, was a family man. He and Aino had six daughters. Most artists, while they are, as I said, outliers, they are outliers from a certain level in society--the upper middle class. Yes, there are working class artists and aristocratic artists, but I suspect that they are the minority. Most come from some level of the middle class, especially considering that this is the largest part of modern societies. All his life Sibelius struggled with the two problems of providing for his family and his overindulgence in cigars and alcohol. He received support from the state and an income from publishing, but this was never quite enough.
Charles Ives' life (1874 - 1954) illustrates the difficulties of an artist in the New World. Though he studied music at Yale, he never seriously attempted to earn a living as a composer. Soon after graduation he entered the insurance business and later on founded his own company. It was Charles Ives who invented the field of estate planning for the wealthy! He composed a great deal of largely experimental music, but stopped around 1927. His manuscripts moldered in a garage and his music was largely ignored until Leonard Bernstein did some important premieres in the 1950s.
In the later 20th century things got even worse because few governments outside of northern Europe provide any pension for their artists, just a few paltry and sporadic grants. Nearly every composer has to follow the path of academia, teaching theory and composition in a conservatory or university. This does not seem to lead to much brilliant, creative work! The outstanding composers all seem to be outside that model. Philip Glass worked at lower class jobs like driving a taxi, being a plumber and a furniture mover and he did this well into his forties when he started getting enough commissions to scrape by. He lived a largely bohemian life. Steve Reich seems to have found enough patrons to subsist until he formed his ensemble and began doing a lot of performances and recordings.
Stravinsky seems to have been the last composer to have achieved enough fame in society to generate a good income. Early on he got significant commissions from Diaghilev and continued to write well-received ballets for decades after. He got a lot of important commissions and also derived income from performances, recordings and a long series of books written with Robert Craft. Alas, with the exception of Philip Glass, who has followed a similar path in his prolific writing for theatre and film, this seems out of reach for anyone else.
One siren call these days seems to be to figure out a way to emulate or share in the bounty of popular music where it is possible to earn fantastic sums of money. But while the occasional popular artist might dabble in art music and the occasional classical composer might dabble in popular music, the two seem largely unreconcilable.
It ain't easy!
Let's listen to a fairly early piece by Charles Ives. This is Central Park in the Dark, composed in 1906. This the Northern Sinfonia conducted by James Sinclair: