Chicago market
I live in Chicago, near DePaul. Not sure about the market for CFI's in Chicago, but there are really not any airports easy to get to using public transportation, except MDW and ORD. With Meigs closed, your best alternative would probably be Palwaukee. You could take a Metra train out to Wheeling, but it is still at least a mile or two from the train station to the airport. Unless you work in the city, you really need a car to do most stuff in surrounding areas.