Compared to the rest of the Greater Portland market, the Tualatin region has smaller rates, so you should have no trouble finding a great deal in this discounted region.
In the last 90 days, 10 listings have been made available, which means leases most likley are leasing quickly. You'll want to be prepared to make an offer immediately. 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 2,380 sqft. Most buildings in this market were built in 2002 and are Class A.