The typical asking rate per listing is in the $10's per square foot per year. The Ballwin region is seeing a a rise in rates. In the last 3 months, the median rate increased $17 per sqft per year. That's a Inf% rise in rent.
In the last 90 days, 8 listings have been posted online, which means new listings most likley are leasing quickly. You'll want to be prepared to make an offer immediately. 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 1,210 sqft. Most properties in this region are around 2 floors. Most buildings in this area were built in 1990 and are Class C.