Does a writer need a day job?
This one does, for many of the usual mundane reasons: spouse, children, house. Maybe there are ways to arrange finances so that a middling productive midlist middle-aged author can support all that, including health insurance and retirement funds, on what he brings in, but if there are, I never figured them out.
I'm currently Director of Marketing for a firm that provides financial services for affordable housing. As I've learned, this is more complex than it might seem at first glance. Our customers are investment banks and large owners of multifamily housing. For a long time, I worked in healthcare marketing. Now I work with people who are closer to the money. It's all useful background, for a writer. It helps that it pays the bills.