The typical asking rate per listing is in the $20's per square foot per year. The Duncanville region is going through a a rise in rates. In the last 3 months, the median rate increased $2 per sqft per year. That's a 10% rise in rent.
Compared to the rest of the DFW Metroplex market, the Duncanville region has less expensive rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 4 listings have been posted online, which means office spaces are probably leasing quickly. You'll want to be prepared to tour spaces as quick as possible. 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 1,000 sqft. Most buildings in this market are close to 1 floors. Most buildings in this region were built in 1989 and are Class A.