The typical asking rate per listing is in the $20's per square foot per year. The Des Peres region is going through a a rise in rates. In the last 3 months, the median rate went up $24 per sqft per year. That's a Inf% rise in rent.
In the last 90 days, 4 listings have come on the market, which means leases are probably leasing quickly. You'll want to be prepared to make an offer immediately. About 50% of the available leases in the Des Peres are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet available, so finding a space for a small business might be tough.
Even though the median size is 2,790 sqft, there are still 0 spaces below 2,000 sqft. Most properties in this region are approximately 2 floors. Most buildings in this market were built in 1987 and are Class A.