From the Portland website:

"Current operators of all short-term rentals can come and register beginning on October 16th. All island, owner-occupied, and tenant-occupied units and non-owner occupied units should contact the city and register beginning on October 16.

The City Council placed a cap of 300 on the number of non-owner occupied short-term rental units on the mainland. Because of this cap, when registering, preference will be given to non-owner occupied STR operators who can demonstrate they have been in operation on or before April 26, 2017. Registration will be taken on a first-come first-served basis through November 30 to qualify within the cap."

Re fees: