On average, listings lease in the $10's per square foot per year. The Butte submarket is going through a a rise in rates. In the last 3 months, the median rate rose $0 per sqft per year. That's a 1% rise in rent.
In the last 90 days, 13 listings have been posted online, which means leases most likley are leasing quickly. You'll want to be prepared to tour spaces as quick as possible. About 8% of the listings in the Butte are subleases, so you will probably need to sign a longer term lease with the landlord directly. 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 1,200 sqft. Most properties in this market are around 0 stories. Most buildings in this market were built in 1978.