Maine’s largest city is considering a significant increase in the fees charged to property owners who offer short-term rentals through services such as Airbnb. Portland Mayor Ethan Strimling says, “We simply aren’t charging enough in relation to the impact that the short-term rentals are having on the rental market.” Portland Mayor Ethan Strimling’s proposal would raise registration fees by as much as 400 percent in some cases over the current schedule.