On average, listings lease in the $30's per square foot per year. The Webster Groves region is seeing a a rise in rates. In the last 3 months, the median rate went up $15 per sqft per year. That's a 75% rise in rent.
In the last 90 days, 2 listings have been made available, which means new availabilities most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. 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 160 sqft. Most buildings in this area are around 2 floors. Most buildings in this market were built in 1968 and are Class B.