Most listings are in the $10's per square foot per year. The Mishawaka region is going through a a rise in rates. In the last 3 months, the median rate rose $3 per sqft per year. That's a 15% increase in rent.
In the last 90 days, 32 listings have been posted online, which means leases are probably going fast. You'll want to be prepared to make an offer immediately. About 56% of the listings in the Mishawaka are subleases, so you might be able to sign a shorter term by taking over a previous lease. 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 2,130 sqft. Most buildings in this market are around 2 stories. Most buildings in this region were built in 1991 and are Class A.