Compared to the rest of the Chicagoland market, the Riverside region has greater rates, and you'll have to negotiate above asking rent to be in this hot submarket.
In the last 90 days, 1 listings have been posted online, which means listings most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 100% of the listings in the Riverside 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 available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,550 sqft. Most buildings in this region were built in 1871 and are Class B.