On average, listings lease in the $10's per square foot per year. The Pennington County region is going through a a boost in rates. In the last 3 months, the median rate rose $2 per sqft per year. That's a 12% increase in rent.
In the last 90 days, 11 listings have come on the market, which means new listings most likley are leasing quickly. You'll want to be prepared to make an offer immediately. 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 1,800 sqft. Most properties in this region are close to 3 stories. Most buildings in this market were built in 1990 and are Class B.