Most listings are in the $20's per square foot per year. The Portland region is seeing a an increase in rates. In the last 3 months, the median rate went up $1 per sqft per year. That's a 7% increase in rent.
In the last 90 days, 44 listings have been posted online, so you'll want to check back regularly for new listings. About 2% of the available leases in the Portland are subleases, so you will probably have to consider a longer term lease. 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 1,340 sqft. Most properties in this market are around 3 floors. Most buildings in this market were built in 1900 and are Class B.