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 discounted submarket.
In the last 90 days, 30 listings have been listed, which means leases most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 50% of the listings in the Northbrook 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 1,630 sqft. Most properties in this area are close to 4 stories. Most buildings in this area were built in 1980 and are Class A.