There is such a wide variation on Long island (If you are asking about Long Island, NY anyway), that no one can give you that answer. Each town is different, the price would be different for a strip mall vs. on a main street, main street vs. side street, also, larger spaces generally go for less per sq ft than smaller spaces. Too many variables here to answer your question.
We recently had a space we were trying to rent. We ended up giving it to a broker, got a tenant right away to pay more than we expected. If you have a property to rent, try going that route. it was worth every penny.