The typical asking rate per listing is in the $10's per square foot per year. The Keller submarket is experiencing a decline in rates. In the last 3 months, the median rate fell $1 per sqft per year. That's a 8% decline in rent.
Compared to the rest of the DFW Metroplex market, the Keller submarket has smaller rates, so you should have no trouble finding a great deal in this undervalued submarket.
In the last 90 days, 3 listings have come on the market, which means new listings are probably leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 200% of the listings in the Keller 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 available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,550 sqft. Most properties in this market are approximately 1 stories. Most buildings in this area were built in 2006 and are Class B.