Most listings are in the $20's per square foot per year. The Portland region is going through a a rise in rates. In the last 3 months, the median rate increased $28 per sqft per year. That's a Inf% increase in rent.
In the last 90 days, 5 listings have been posted online, which means spaces 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 280 sqft. Most properties in this market are around 2 stories. Most buildings in this area were built in 1987 and are Class B.