For the last two years, Spain has been in the thick of a massive housing crisis. There are somewhere between 700,000 and a million new, unsold homes in the country. (The U.S., by contrast, with five times the population of Spain, has only 145,000 new unsold homes.) Spanish banks hold nearly 200 billion euros worth of bad mortgage loans. So Spain is offering a deal. Buy a house worth more than the mean home price and receive something that had been, until now, priceless: Spanish residency papers. Spain isn't the first European country that's tried to stimulate the housing market...