Most listings are in the $20's per square foot per year. The St. Louis County region is seeing a an increase in rates. In the last 3 months, the median rate increased $2 per sqft per year. That's a 9% rise in rent.
In the last 90 days, 76 listings have been listed, 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 have to consider a longer term lease. 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 1,410 sqft. Most properties in this market are around 3 floors. Most buildings in this area were built in 1955 and are Class A.