AutoSlash points to a deal from Advantage, rental cars in Chicago from $62 per week all-in, from July 24 through the end of August. As they note, a 28-day rental is only $250, so less than many lease payments without the ongoing obligation.
Book here. Once you get results to come up you can change the search to your preferred dates and preferred Chicago-area airport.
Update: The deal is also available in Louisville.