On average, listings lease in the $20's per square foot per year. The Southlake submarket is going through a a rise in rates. In the last 3 months, the median rate rose $30 per sqft per year.
Compared to the rest of the DFW Metroplex market, the Southlake region has greater rates, and you'll have to negotiate above asking rent to be in this hot region.
In the last 90 days, 27 listings have been made available, which means office spaces might be leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 100% of the listings in the Southlake are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 2,230 sqft. Most buildings in this area are around 1 stories. Most buildings in this market were built in 2002 and are Class A.