The typical asking rate per listing is in the $30's per square foot per year. The Riverhead region is going through a an increase in rates. In the last 3 months, the median rate increased $32 per sqft per year.
In the last 90 days, 9 listings have come on the market, which means spaces are probably going fast. You'll want to be prepared to tour spaces as quick as possible. 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 1,950 sqft. Most buildings in this market are approximately 1 stories. Most buildings in this area were built in 1990 and are Class B.