Career Change - Full-time CFI: Average Flight Hours per year?

Background: I'm currently 30 years old with my IFR and about 190 hrs
TT. Currently working as a systems administrator/programmer, but
weighing my options are if I were to try to make a career out of
aviation. Yeah - crazy, right? Try sitting in front of a monitor for
8 hours a day in a cubicle in a building with no windows! It makes
mowing lawns sound like a good career move...

Anyway, spending a year or two as a CFI seems like the common thing
most folks do in order to build time. From poking around in the
newsgroups, it seems as though if a new CFI were pulling in around
$20k for full-time instructing, he would be considered a rich man! I
could have survived on $20k about 5 years ago, but with a wife and a
baby on the way, that's just not going to cut it.

If I could build up enough hours to get hired on somewhere making
$25k-$30k, that wouldn't be as unrealistic financially, and I could
pad it a bit with some contract work here-and-there.

So rather than chuck my current job right away, I figured I'd do a
little comparison and see how realistic I was being. How many hours
could I build up per year (and how much that would cost) if I stayed
at my current job and flew on the weekends versus how many hours I
would get (and how much money I would lose) if I instructed full-time.

So, all of that to tell you the origin of what I am asking:
Generally, how many hours can a full-time CFI expect to fly in a year?