Most listings are in the $10's per square foot per year. The Waukesha submarket is seeing a decline in rates. In the last 3 months, the median rate fell $7 per sqft per year. That's a 29% decline in rent.
In the last 90 days, 8 listings have been made available, which means leases most likley are going fast. You'll want to be prepared to make an offer immediately. About 100% of the listings in the Waukesha are subleases, so you might be able to find a shorter term or below market rent. There aren't many listings below 2,000 square feet posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,330 sqft. Most properties in this region are close to 1 floors. Most buildings in this area were built in 1983 and are Class B.