Most listings are in the $10's per square foot per year. The River Park submarket is going through a a boost in rates. In the last 3 months, the median rate went up $20 per sqft per year.
In the last 90 days, 16 listings have been posted online, which means leases are probably going fast. You'll want to be prepared to tour spaces as quick as possible. About 63% of the listings in the River Park 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 posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 2,000 sqft. Most properties in this region are close to 1 stories. Most buildings in this market were built in 1984 and are Class B.