The typical asking rate per listing is in the $10's per square foot per year. The Duncan region is experiencing a a rise in rates. In the last 3 months, the median rate rose $15 per sqft per year.
In the last 90 days, 4 listings have been posted online, which means 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 available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,100 sqft. Most properties in this region are close to 2 stories.