The typical asking rate per listing is in the $50's per square foot per year. The Portland region is going through a a boost in rates. In the last 3 months, the median rate increased $50 per sqft per year.
In the last 90 days, 0 listings have been listed, which means leases are probably going fast. You'll want to be prepared to make an offer immediately. About NaN% of the available leases in the Portland are subleases, so you will probably need to sign a longer term lease with the landlord directly. 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 1,140 sqft. Most properties in this area are around 2 floors. Most buildings in this region were built in 1979 and are Class B.