Most listings are in the $10's per square foot per year. The Glenwood Springs region is going through a a rise in rates. In the last 3 months, the median rate rose $18 per sqft per year.
In the last 90 days, 2 listings have been posted online, which means leases are probably going fast. You'll want to be prepared to tour spaces as quick as possible. About 50% of the available leases in the Glenwood Springs are subleases, so you might be able to snag a great spot on a short term. 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 2,260 sqft. Most buildings in this area were built in 1983.