Which MBA programs in the Chicago area are "older applicant" friendly? I am defining older applicant as being between 40 and 50.

This kind of question comes up occasionally on this board - I'd encourage you to read through these threads to start with:

http://www.find-mba.com/board/35540
http://www.find-mba.com/board/29872

Even the top tier programs admit 40+ year-olds, but not at huge rates. But this more reflects the role that full-time MBAs play for people: they're often used to switch job functions or industries, and younger people tend to want to to this more than older folks who are more likely to be settled in a career path.

In short, no full-time MBA program is going to be aimed specifically at older applicants, nor is any going to be "older friendly," to a huge degree in comparison to others. It's simply the nature of the degree that you'll be an outlier most full-time programs (versus part-time and executive programs.) The key would be to demonstrate that your goals mesh with what the business school can provide.