Very few writers can support themselves in style with their writing unless they are willing to turn out porn or copies of whatever is hot at the moment. That is not "writing". That is work.
If you aim for publication, be sure to check out the market, because publishers want a sure thing---and that means something very much like something else that has made a lot of money. A talented writer can write anything, so if you need the money, do not hesitate to write what you think the paying audience wants. But do not expect to be rewarded by publishers for your creativity and do not expect to get a lot of satisfaction from writing the formula fiction they do want. Also remember that when a publisher rejects your work, he is not rejecting your soul. He thinks the book won't make any money.
I am lucky to have a "day job" that I love---I am a family physician at a public clinic that provides health care for the needy. I make less than a lot of doctors in private practice, but I make much more than I would if I tried to support myself writing. If you really want to make money doing something creative, consider art. I do a little art as a hobby, and I make much more money from that than I do from writing---even though writing is my avocation. People are more than willing to pay cold, hard cash for the privilege of owning something that is one of a kind.
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