The typical asking rate per listing is in the $10's per square foot per year. The Beaverton region is going through a decrease in rates. In the last 3 months, the median rate fell $3 per sqft per year. That's a 12% decline in rent.
Compared to the rest of the Greater Portland market, the Beaverton region has less expensive rates, so you should have no trouble finding a great deal in this discounted region.
In the last 90 days, 30 listings have been posted online, which means office spaces most likley are going fast. You'll want to be prepared to make an offer immediately. About 3% of the listings in the Beaverton are subleases, so you will probably need to consider the implications of signing a direct lease with the building. 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 1,690 sqft. Most properties in this region are approximately 1 floors. Most buildings in this market were built in 1987 and are Class A.