Most listings are in the $10's per square foot per year. The Janesville region is going through a a rise in rates. In the last 3 months, the median rate increased $18 per sqft per year.
In the last 90 days, 31 listings have been posted online, which means new availabilities are probably going fast. You'll want to be prepared to tour spaces as quick as possible. About 10% of the available space in the Janesville are subleases, so you will probably have to focus your search on direct office leases. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,100 sqft. Most properties in this region are approximately 2 stories. Most buildings in this region were built in 1980 and are Class B.