On average, listings lease in the $20's per square foot per year. The Northbrook region is seeing a an increase in rates. In the last 3 months, the median rate increased $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 undervalued region.
In the last 90 days, 38 listings have come on the market, which means spaces are probably going fast. You'll want to be prepared to make an offer immediately. About 3% of the listings in the Northbrook 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.
The standard measurement for office space in this area is around 1,610 sqft. Most buildings in this area are around 4 floors. Most buildings in this region were built in 1980 and are Class A.