In Minnesota they have a tax for homes that are not lived in full time for 6+ months of the year. I wonder if something like that would help curb the Airbnbs and investment purchases that happen so often in places like Lisbon.

Building more homes would help, of course, but all the expats want to live in the historic area (it seems), so those prices will still be driven up. From my visit there, a lot of the older folks were the ones still living in the old downtown area, waiting to be priced out of their homes.