Of the many artist/photographers I know most have/need a way to supplement their income. It was only after years of work that Ansel made a good income from selling prints alone. The entire Weston clan, even Edward worked at other things, although Edwards work was with the WPA and was reduced to a documentary photographer, which supplemented their income.
Even back in 2001 or so Dick Arentz told me that he was profoundly happy he had a 401k that supported his lifestyle, not lavish by any means, and told others not to quit their day job.
One problem I have is that as for my day job, I used to love what I did, now it's a somewhat soul sucking endeavor to do the daily grind. I have found a place though, through my art, whether I teach, create images, putter in the darkroom, or churn out prints for a huge show, that I want to protect as my place to go when I need to create.
For years I have vacillated back and forth as to what I would do if I had the opportunity to focus only on photography. I would really lose a large part of who I am if I were to ruin through the need to meet monetary requirements what I do.
I do sell my work, but with the economy, it has been quite a challenge the last couple years.
For what it's worth.