On average, listings lease in the $30's per square foot per year. The Kent submarket is going through a a boost in rates. In the last 3 months, the median rate increased $5 per sqft per year. That's a 18% rise 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 discounted submarket.
In the last 90 days, 10 listings have come on the market, which means office spaces might be leasing quickly. You'll want to be prepared to make an offer immediately. About 130% 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 posted, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,180 sqft. Most buildings in this market are close to 1 stories. Most buildings in this area were built in 1987 and are Class A.