The typical asking rate per listing is in the $20's per square foot per year. The St. Louis County region is going through a an increase in rates. In the last 3 months, the median rate went up $5 per sqft per year. That's a 24% increase in rent.
In the last 90 days, 97 listings have come on the market, so you'll want to check back regularly for new listings. About 1% of the available space in the St. Louis County are subleases, so you will probably need to consider the implications of signing a direct lease with the building. 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 3,660 sqft, there are still 0 leases below 2,000 sqft. Most buildings in this region are approximately 3 floors. Most buildings in this area were built in 1964 and are Class B.