Most listings are in the $20's per square foot per year. The St. Louis County submarket is going through a decrease in rates. In the last 3 months, the median rate decreased $1 per sqft per year. That's a 5% decline in rent.
In the last 90 days, 258 listings have been listed, so you'll want to check back regularly for new listings. About 5% of the listings 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 available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 2,000 sqft. Most properties in this market are close to 2 floors. Most buildings in this area were built in 1983 and are Class B.