I actually do some charter work for ONU through their AD's office and associates. I am very familiar with the university and the general area. The campus is beautiful and everybody is pretty laid back. You do have to put up with the typical christian college stuff, but otherwise it is a nice place to be. One bonus, the Chicago Bears have their summer camp at ONU.
Well that is not what you asked, so here goes. IKK is the the nearest airport to campus. Probably about a 25 to 30 minute drive. Not much goes on at IKK. The flight school is named K3 Aero II. The guy that owns it is a doctor and basically has the business to support his flying habit. He has a guy that is 70+ and a DE in the area running the place. This guy is a nice guy, but at the same time kind of a hard a$$. The school has been pretty slow the last couple years. I think they have been keeping 1 full time and 1 part time instructor on staff, plus the DE guy. If you timed it right you just might be able to get a job there. My guess is that you would not really make much money because of the low amount of student traffic, but you would probably fly enough to stay sharp. These guys have C152s, C172s, an Arrow, and a Twin Comanche.
Other options might be JOT. It is about a 40 minute drive to JOT. There is a school/shop called JF Aviation. The guy that runs it is kind of a weird guy (never smiles), but all and all a good operation. They stay pretty busy and you could probably do a lot of flying there. They have Cessna 152s, 172s, and a 182. No twins and no retracts. Your only other option would be LOT. Last I checked the only school was the University (Lewis). I don't know if they take outside instructors, but you could always check. You might also find C56 and 1C2. Don't bother. One has no school and the other is about to close. Good luck.