On average, listings lease in the $50's per square foot per year. The Valley Stream submarket is going through a a rise in rates. In the last 3 months, the median rate increased $11 per sqft per year. That's a 29% rise in rent.
In the last 90 days, 2 listings have been made available, which means leases are probably going fast. You'll want to be prepared to make an offer immediately. 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 750 sqft. Most buildings in this region were built in 1983 and are Class B.