Compared to the rest of the Seattle Metropolitan Area market, the Burien region has smaller rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 2 listings have come on the market, which means new availabilities most likley are leasing quickly. You'll want to be prepared to make an offer immediately. About 50% of the available space in the Burien are subleases, so you might be able to sign a shorter term by taking over a previous lease. There aren't many listings below 2,000 square feet on the market, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 1,280 sqft. Most buildings in this area are approximately 1 floors. Most buildings in this market were built in 1980 and are Class B.