Most listings are in the $10's per square foot per year. The Milwaukie submarket is experiencing a a rise in rates. In the last 3 months, the median rate rose $15 per sqft per year. That's a Inf% increase in rent.
Compared to the rest of the Greater Portland market, the Milwaukie region has less expensive rates, so you should have no trouble finding a great deal in this depreciated region.
In the last 90 days, 2 listings have come on the market, which means listings 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 available, so finding a space for a small business might be tough.
The standard measurement for office space in this area is around 690 sqft. Most properties in this area are around 2 floors. Most buildings in this market were built in 1988 and are Class B.