Most listings are in the $20's per square foot per year. The River Forest region is seeing a a rise in rates. In the last 3 months, the median rate went up $24 per sqft per year. That's a Inf% increase in rent.
Compared to the rest of the Chicagoland market, the River Forest submarket has smaller rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 1 listings have been posted online, which means leases might be leasing quickly. You'll want to be prepared to tour spaces as quick as possible. 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 1,500 sqft.