The typical asking rate per listing is in the $10's per square foot per year. The Sumner submarket is experiencing a a rise in rates. In the last 3 months, the median rate increased $15 per sqft per year.
Compared to the rest of the Seattle Metropolitan Area market, the Sumner region has lower rates, so you should have no trouble finding a great deal in this undervalued region.
In the last 90 days, 2 listings have come on the market, which means spaces are probably 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.
Even though the median size is 4,000 sqft, there are still 0 office spaces below 2,000 sqft. Most buildings in this area are approximately 2 stories. Most buildings in this area were built in 1979 and are Class B.