On average, listings lease in the $20's per square foot per year. The Northbrook region is seeing a a rise in rates. In the last 3 months, the median rate went up $0 per sqft per year. That's a 0% rise in rent.
Compared to the rest of the Chicagoland market, the Northbrook region has lower rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 38 listings have been posted online, which means new availabilities most likley are going fast. You'll want to be prepared to make an offer immediately. About 3% of the office spaces in the Northbrook are subleases, so you will probably need to consider the implications of signing a direct lease with the building. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,610 sqft. Most buildings in this region are close to 4 stories. Most buildings in this region were built in 1980 and are Class A.