On average, listings lease in the $20's per square foot per year. The Ballwin region is seeing a an increase in rates. In the last 3 months, the median rate increased $4 per sqft per year. That's a 22% increase in rent.
In the last 90 days, 6 listings have been made available, which means listings are probably leasing quickly. You'll want to be prepared to make an offer immediately. 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 2,030 sqft. Most properties in this area are close to 3 floors. Most buildings in this market were built in 1972 and are Class B.