Most listings are in the $20's per square foot per year. The Willowbrook submarket is going through a an increase in rates. In the last 3 months, the median rate increased $4 per sqft per year. That's a 21% increase in rent.
Compared to the rest of the Chicagoland market, the Willowbrook submarket has lower rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 6 listings have been made available, which means office spaces might be leasing quickly. You'll want to be prepared to make an offer immediately. About 17% of the office spaces in the Willowbrook are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,740 sqft. Most buildings in this market are close to 1 floors. Most buildings in this region were built in 1979 and are Class B.