The typical asking rate per listing is in the $20's per square foot per year. The Westmont region is going through a an increase in rates. In the last 3 months, the median rate went up $3 per sqft per year. That's a 19% increase in rent.
Compared to the rest of the Chicagoland market, the Westmont region has smaller rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 18 listings have come on the market, which means leases most likley are going fast. You'll want to be prepared to make an offer immediately. 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 1,650 sqft. Most properties in this area are approximately 1 stories. Most buildings in this region were built in 1988 and are Class A.