Most listings are in the $10's per square foot per year. The Missoula region is seeing a decline in rates. In the last 3 months, the median rate fell $1 per sqft per year. That's a 4% decrease 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 tour spaces as quick as possible. 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 1,750 sqft. Most properties in this market are close to 1 floors. Most buildings in this area were built in 1981 and are Class A.