Madrid, Oct 24 (Reuters) - Last year Madrid's city and regional governments sold almost 5,000 rent-controlled flats to private equity investors including Goldman Sachs and Blackstone. At the time, the tenants were told their rental conditions would remain the same. But as old contracts expire, dozens of people have received demands for higher rent, been told their rents will increase dramatically, been threatened with eviction or moved out to escape the insecurity.