Most listings are in the $20's per square foot per year. The Missouri submarket is going through a a boost in rates. In the last 3 months, the median rate went up $1 per sqft per year. That's a 6% increase in rent.
In the last 90 days, 882 listings have been listed, so you'll want to check back regularly for new listings. About 3% of the listings in the Missouri are subleases, so you will probably need to sign a longer term lease with the landlord directly. 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 2,500 sqft. Most buildings in this market are around 2 floors. Most buildings in this market were built in 1984 and are Class B.