The typical asking rate per listing is in the $20's per square foot per year. The Polk County submarket is going through a a rise in rates. In the last 3 months, the median rate rose $23 per sqft per year.
In the last 90 days, 3 listings have been made available, which means spaces are probably leasing quickly. 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 640 sqft. Most buildings in this market are close to 1 stories. Most buildings in this area were built in 1976 and are Class B.