The typical asking rate per listing is in the $20's per square foot per year. The Smithtown submarket is going through a a boost in rates. In the last 3 months, the median rate increased $25 per sqft per year.
In the last 90 days, 4 listings have come on the market, which means new listings most likley are going fast. You'll want to be prepared to make an offer immediately. About 175% of the listings in the Smithtown are subleases, so you might be able to snag a great spot on a short term. 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 800 sqft. Most buildings in this market are close to 2 stories. Most buildings in this region were built in 1987 and are Class B.