Most listings are in the $10's per square foot per year. The River Park region is going through a decline in rates. In the last 3 months, the median rate fell $3 per sqft per year. That's a 13% decrease in rent.
In the last 90 days, 14 listings have been made available, which means listings most likley are going fast. 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 1,740 sqft. Most buildings in this region are approximately 2 floors. Most buildings in this region were built in 1985 and are Class B.