"Retirement" in the second decade of the 21st century doesn't necessarily mean stopping to work. Rather, it could just mean doing different kind of work to keep maintaining a lifestyle.
One of those options is what is being called "Landlord Nation." Those preparing for retirement or are already retired buy up single family homes they can rent out. Here is the coverage in Bloomberg about this trend.
About 37% of households now rent versus buy. For Baby Boomers like myself, we already sold our house. We don't want the uncertainties associated with ownership any more. So, we rent.
At the other end, Millennials usually can't afford the down payment. And with their student loans and jobs which pay peanuts, they recognize they better stick with renting.
With so much demand for rentals, landlords have the upper hand in setting the initial rent and then increasing it annually. So, rentals are a good business, at least now.