I just realized that I never really answered my own questions about whether or not writing = job or hobby (Please read that post first, or I'm afraid this one won't make sense) (and this is my opinion for me--I do think the answer to the question is entirely an individual response).
For me: I consider myself as having two jobs. One pays, one doesn't. In my own head, that's the way it is--I am a teacher and a writer. If I take a break from teaching (much) later to make/raise babies, I think I will introduce myself first as writer, then as housewife--primarily because I define job as money, and whichever job earns the most money (or has the potential to earn the most money) is the one I define as my primary job.
I don't think of writing as a hobby. If I defined it for myself as that, then I am afraid that I would not take it as seriously. I'm looking at my writing career as the old adage of "dress for the job you want." In my case, I'm acting like the job I want: blog, network, conference, writing schedule, crit groups, etc. Writing practice = building my resume.