Most listings are in the $20's per square foot per year. The Southwest Side region is going through a an increase in rates. In the last 3 months, the median rate increased $21 per sqft per year.
Compared to the rest of the Chicagoland market, the Southwest Side submarket has lower rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 6 listings have come on the market, which means leases most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. About 350% of the available leases in the Southwest Side 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 1,270 sqft. Most properties in this market are close to 1 floors. Most buildings in this region were built in 1950 and are Class A.