The typical asking rate per listing is in the $20's per square foot per year. The Portland region is experiencing a a boost in rates. In the last 3 months, the median rate went up $28 per sqft per year. That's a Inf% increase in rent.
In the last 90 days, 5 listings have come on the market, which means new listings are probably going fast. You'll want to be prepared to make an offer immediately. 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 280 sqft. Most buildings in this area are around 2 stories. Most buildings in this area were built in 1987 and are Class B.