Most listings are in the $20's per square foot per year. The Des Peres region is going through a decline in rates. In the last 3 months, the median rate decreased $2 per sqft per year. That's a 7% decrease in rent.
In the last 90 days, 8 listings have come on the market, which means listings are probably leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 25% of the office spaces in the Des Peres are subleases, so you might be able to snag a great spot on a short term. 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 1,310 sqft. Most properties in this market are close to 2 floors. Most buildings in this region were built in 1987 and are Class B.