The typical asking rate per listing is in the $10's per square foot per year. The Belleville submarket is going through a an increase in rates. In the last 3 months, the median rate increased $1 per sqft per year. That's a 7% rise in rent.
In the last 90 days, 7 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 1,080 sqft. Most buildings in this market are close to 1 stories. Most buildings in this area were built in 1989 and are Class B.