On average, listings lease in the $20's per square foot per year. The River West region is going through a a boost in rates. In the last 3 months, the median rate rose $25 per sqft per year.
Compared to the rest of the Chicagoland market, the River West submarket has lower rates, so you should have no trouble finding a great deal in this depreciated submarket.
In the last 90 days, 4 listings have come on the market, which means spaces might be going fast. You'll want to be prepared to make an offer immediately. About 25% of the office spaces in the River West 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 available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,470 sqft. Most buildings in this market are around 3 floors. Most buildings in this area were built in 1998 and are Class B.
Not much of the real estate is used for commercial space, so it might be hard to find office space. Education is the dominant industry in this market. Most of the folk of River West work from home. Commuting approximately 15 minutes a day is the norm for those who opt to reside in this part of town.