Expats can be helpful to a country like Portugal but it has to be done correctly. And of course it hasn't. What Portugal needs to do is:

1. Ban Airbnb and other short-term housing other than renting out a room in your house;

2. Provide a huge stock of social housing, meaning housing at an affordable price only available to natives; and

3. Restrict foreign ownership of huge swathes of the country. This could be as simple as "new construction only".

Capitalism simply does not work where there's inelastic demand. it creates a regime where money is extracted from the poorest and most vulnerable by withholding basic human needs in the interests of profit for a few.

EDIT: qualified the AirBnB restriction to only what it should be for, meaning renting out a room in your house, not running an illegal hotel.