The typical asking rate per listing is in the $20's per square foot per year. The Willowbrook submarket is seeing a an increase in rates. In the last 3 months, the median rate increased $21 per sqft per year.
Compared to the rest of the Chicagoland market, the Willowbrook region has smaller rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 6 listings have been posted online, which means spaces most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 150% of the available leases 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 available, 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 properties in this market are close to 1 floors. Most buildings in this area were built in 1979 and are Class B.