On average, listings lease in the $10's per square foot per year. The Carpentersville region is going through a a rise in rates. In the last 3 months, the median rate went up $20 per sqft per year.
Compared to the rest of the Chicagoland market, the Carpentersville submarket has lower rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 16 listings have been posted online, which means new availabilities 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 1,760 sqft. Most buildings in this area were built in 2002.