On average, listings lease in the $40's per square foot per year. The McKinney region is going through a a rise in rates. In the last 3 months, the median rate went up $18 per sqft per year. That's a 77% increase in rent.
Compared to the rest of the DFW Metroplex market, the McKinney submarket has greater rates, and you'll need to pay a premium to be in this hot region.
In the last 90 days, 39 listings have been listed, which means office spaces most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 3% of the office spaces in the McKinney are subleases, so you will probably need to consider the implications of signing a direct lease with the building. 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 1,230 sqft. Most buildings in this market are close to 2 floors. Most buildings in this area were built in 2004 and are Class A.