On average, listings lease in the $40's per square foot per year. The Mount Vernon region is going through a an increase in rates. In the last 3 months, the median rate increased $46 per sqft per year.
In the last 90 days, 5 listings have come on the market, which means new availabilities most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. About 100% of the listings in the Mount Vernon are subleases, so you might be able to find a shorter term or below market rent. 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 940 sqft. Most properties in this market are around 3 floors. Most buildings in this area were built in 1945 and are Class A.