On average, listings lease in the $30's per square foot per year. The St. Charles submarket is seeing a a boost in rates. In the last 3 months, the median rate rose $12 per sqft per year. That's a 49% increase in rent.
In the last 90 days, 24 listings have been posted online, which means leases are probably going fast. You'll want to be prepared to make an offer immediately. About 8% of the available leases in the St. Charles are subleases, so you will probably need to sign a longer term lease with the landlord directly. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
Even though the median size is 3,250 sqft, there are still 0 listings below 2,000 sqft. Most properties in this area are close to 1 stories. Most buildings in this region were built in 1993 and are Class B.