It's a smart question. Parking can be very expensive at O'Hare.
If you park at the airport, the farther away you park, the cheaper it is. Stay out of lots A, B, C & D in front of the terminals. Park in one of the lots that is off of Bessie Coleman. There are two, E & F, the one on the west side of the street will bus you to the lot on the east side of the street. In the lot on the east side is the ATS. It's a free Airport Transit System, that will bring you right to the terminals, it runs about every 15 min. Takes a little longer late at night or early in the morning.
There are some lots on Mannheim Rd., south of the airport that are fairly reasonable. The Thrifty Car Rental has airport parking.
For the money, it might be a good idea to stay the night at a hotel & take their shuttle bus to the airport. They will let you leave your car in their parking lot for free. This is a good idea if you are traveling some distance to get to O'Hare. All you need is a flat tire & you could miss your flight. Check out the Best Western O'Hare @ the corner of Higgins (Rt. 72) & Mannheim Rd. Or either of the 2 Rosemont Hyatt Hotels. Do a hotel search for Rosemont, IL That is where all the nice airport hotels are located. Stay out of Franklin Park & hotels south of the airport.
I hope that helps a little. I don't have any prices for you, 'cause I park for free at the airport. (I have to rub it in a little)
Where are you going? (Cayman?) What airline are you flying?
