Just a rough guess would be that, after initial costs, you're looking at a minimum of $500/month if you go 2x/month. Jeeps is right about the school thing too, and IIRC there is even a decent one in the Chicago area...I'll post it up if I can find it.
As far as clubs go: STT and NESBA are the best in the Mid-West, join them, but wait until January to join STT because their memberships are for the calendar year (if you got one now it would expire Dec 31 of this year and you still have to pay the full price). NESBA's membership is good 1 year from the date you join. Also, if you're serious about going a lot, they offer packages at a discounted rate so look into those as well.
Also, I'm assuming you know that you have to have full leathers, a back protector, gloves with a full wrist gauntlet, riding boots (hiking or work boots won't cut it here) and a helmet that is less than 2 years old. You'll also need a trailer (unless you have a pickup) to get your bike to the track and back (especially when you wreck).
This all adds to the initial expense of getting to the track. So for the gear, assuming you have a helmet, you should expect to spend at least another $400-500 and that's assuming you skimp on the leathers. You can spend as much on a trailer as you would like ($200-$2000+++)
would be to buy yourself a '99-'02 SV650 (naked) and make that into a track bike. At every track day I've been to they have been the most popular bike there for a number of reasons: 1) There are tons of parts around so replacing things is relatively cheap when you crash (and you will!) 2) the torque of the v-twin make for an easier learning curve and a more forgiving bike to learn on 3) there are very few plastics to break when you're starting out and lots of aftermarket racing kits if you want to add plastics later (which hold up much better than stocks in wrecks) 4) they aren't a bike that you have to worry about a lot, you can just get out and ride the crap out of them cuz they're practically bullet-proof (as long as you don't wheelie) 5) they just handle tracks very very well and are tons of fun to ride.
At one of the last track days I was at I was talking with a guy there riding an SV and he said that even though he's owned a bunch of Duc's (and still has a Desmo for the street) the SV was still probably his favorite track bike for exactly the reasons I listed above. Anyway, those are my thoughts, hope they help.