The typical asking rate per listing is in the $10's per square foot per year. The O'Fallon region is going through a decline in rates. In the last 3 months, the median rate fell $2 per sqft per year. That's a 9% decrease in rent.
In the last 90 days, 31 listings have been made available, which means new availabilities are probably going fast. You'll want to be prepared to tour spaces as quick as possible. About 35% of the available leases in the O'Fallon are subleases, so you might be able to find a shorter term or below market rent. 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 13,260 sqft, there are still 0 spaces below 2,000 sqft. Most buildings in this market are approximately 2 floors. Most buildings in this market were built in 2003 and are Class A.