The typical asking rate per listing is 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 went up $26 per sqft per year. That's a 133% rise in rent.
In the last 90 days, 5 listings have been listed, which means new listings are probably going fast. You'll want to be prepared to make an offer immediately. About 160% of the available space 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 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 1,400 sqft. Most properties in this market are approximately 3 floors. Most buildings in this region were built in 1948 and are Class A.