When people say they want to be writers, that can mean many things; there are many kinds of writers to be.
There's journalism, technical writing, advertising. There are educational materials and novels and poems, mysteries and biographies, memoirs and instruction books, screenplays and short stories. At some point a writer gravitates toward a genre and an audience.
Along the way, writers also discover what they expect and hope for in terms of pursuing commercial success. There are writers publishing their own work, bringing out multiple books a year, figuring out how to get their work edited and marketed and formatted. There are writers who publish poems in a local newsletter for free and find it a happy addition to their lives, but they make their living in other ways. There are writers whose chief aim is to do something new with language or form, and writers whose chief aim is to reach a large general audience.There are writers everywhere along these spectra, writers with many different goals.
My own expectations and desires have changed over the past few years. I've come to see how much writing vs. everything else (editing, marketing, selling, teaching, etc.) I want to do. I've come to learn where I want writing to fit into my life. I've come to the point where what I have and what I want are much more closely aligned. I've thought about how I want to spend my time and energy.
Sometimes I read writing advice about how writers have to do X, Y, and Z to be successful, when what the advice-giver really means is that X, Y, and Z gave him the kind of success he wanted. There is a natural variation in whether X, Y, and Z will produce the same results for every writer who wants that brand of success. But before that, a writer can ask: Is that the career I even want? Or does my ideal career look somewhat different?