On average, listings lease in the $20's per square foot per year. The Westchester submarket is going through a a boost in rates. In the last 3 months, the median rate rose $24 per sqft per year.
Compared to the rest of the Chicagoland market, the Westchester region has smaller rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 48 listings have been made available, so you'll want to check back regularly for new listings. About 4% of the office spaces in the Westchester are subleases, so you will probably need to sign a longer term lease with the landlord directly. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
Even though the median size is 2,990 sqft, there are still 0 office spaces below 2,000 sqft. Most buildings in this area are close to 2 stories. Most buildings in this area were built in 1986 and are Class A.