The typical asking rate per listing is in the $0's per square foot per year. The Warrenville region is seeing a decline in rates. In the last 3 months, the median rate fell $28 per sqft per year. That's a 100% decline in rent.
In the last 90 days, 9 listings have been listed, which means leases are probably leasing quickly. 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 sqft. Most properties in this area are around 2 floors. Most buildings in this market were built in 1999 and are Class B.