The typical asking rate per listing is in the $0's per square foot per year. The River Forest submarket is going through a decline in rates. In the last 3 months, the median rate decreased $24 per sqft per year. That's a 100% decline in rent.
In the last 90 days, 0 listings have been listed, which means listings might be leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About NaN% of the listings in the River Forest are subleases, so you will probably have to focus your search on direct office leases. 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 sqft.