As I said, it's not always the case. But in some cities there are shuttered properties, in sometimes prime locations, that are held by non-residents. In some places, like London, it's literally a money laundering who's who. Carrying costs discourage just holding on to property. (I don't know if Portugal has taxes on real property). Increase the carrying costs and the incentive is to rent or sell. That being said, you can't do much about the location of the mountains or the sea.
