Most listings are in the $20's per square foot per year. The Lower Arapahoe region is going through a an increase in rates. In the last 3 months, the median rate went up $26 per sqft per year.
In the last 90 days, 0 listings have been listed, which means new listings are probably going fast. You'll want to be prepared to make an offer immediately. About NaN% of the available leases in the Lower Arapahoe are subleases, so you will probably need to consider the implications of signing a direct lease with the building. 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 2,450 sqft. Most buildings in this area were built in 1930.