The typical asking rate per listing is in the $10's per square foot per year. The Sumner region is seeing a an increase in rates. In the last 3 months, the median rate rose $15 per sqft per year.
Compared to the rest of the Seattle Metropolitan Area market, the Sumner submarket has less expensive rates, so you should have no trouble finding a great deal in this discounted submarket.
In the last 90 days, 2 listings have been listed, which means leases most likley are going fast. You'll want to be prepared to tour spaces as quick as possible. About 250% of the listings in the Sumner 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.
Even though the median size is 4,000 sqft, there are still 0 listings below 2,000 sqft. Most buildings in this area are approximately 1 stories. Most buildings in this area were built in 1995 and are Class B.