On average, listings lease in the $30's per square foot per year. The Mount Kisco submarket is seeing a a boost in rates. In the last 3 months, the median rate increased $4 per sqft per year. That's a 12% rise in rent.
In the last 90 days, 3 listings have been made available, which means leases are probably leasing quickly. You'll want to be prepared to make an offer immediately. 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 1,800 sqft. Most buildings in this area were built in 1986 and are Class B.