I do not play poker professionally... but unlike a lot of the these responses, I don't think it'd be a bad thing to do IF planned out properly and starting with both a sufficient bankroll and sufficient money stashed on the side for expenses (say for a year) in case things dont go as planned. I guess I just don't get people who can make 100k+ and have fun while doing it and then say they want to move onto different things. Good luck making 100k+ in a real job right out of school.
Anyway as for me A monthly average is hard to say, like SJay said because of the varience.
So far this year my #s look like this (nothing special)
Jan: +3.2k
Feb: +2.4k
Mar: -1.6k
April: +.7k (so far)
although these #s could have easily took a 3k swing in the positive if I had avoided 3 total hands
I've also begun playing a bit more online poker lately, and although I dont have a month breakdown, my yearly figure is +1220 at this point
My biggest winning month in the last 2 years is +5.8k and biggest loser is -2.3k