Most listings are in the $20's per square foot per year. The St. Louis County submarket is going through a an increase in rates. In the last 3 months, the median rate went up $2 per sqft per year. That's a 9% rise in rent.
In the last 90 days, 259 listings have been posted online, so you'll want to check back regularly for new listings. About 5% of the available leases 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 posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 2,480 sqft. Most properties in this area are approximately 2 floors. Most buildings in this area were built in 1983 and are Class B.