Simple rules can fix this and technology can help. Only residents can buy real estate. Only one property per household. They have to live in it at least 6 months a year. The rest of the 6 month they could rent, but only at a long term price. If a rental developer wishes to buy they should be steered in a area where rental development is allowed and encouraged. And then enforce the squatting laws. Because that is hurting the local population as well.