The typical asking rate per listing is in the $30's per square foot per year. The Kent region is going through a an increase in rates. In the last 3 months, the median rate went up $13 per sqft per year. That's a 68% increase in rent.
Compared to the rest of the Seattle Metropolitan Area market, the Kent region has less expensive rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 10 listings have been listed, which means new availabilities are probably leasing quickly. You'll want to be prepared to make an offer immediately. About 120% of the available leases in the Kent are subleases, so you might be able to find a shorter term or below market rent. 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 1,330 sqft. Most buildings in this area are close to 1 floors. Most buildings in this market were built in 1986 and are Class A.