I've seen him say it will prevent landlord exploitation, but by definition - almost any pragmatic appliance of rent control will admit a goal of cheaper month-to-month rent. At present, a lot of rental properties have a monthly payment that are equal to - or sometimes more - than mortgage payments for similar* offerings in the same area.
It then follows logically that if rent control leads to cheaper rent, and a lot of rent costs are presently equal to or more than mortgage payments, then it makes renting affordability easier - and housing affordability is still innately more expensive. Rent control is a rent solution, and I guess it makes RENTAL of housing more affordable - which is good. But it's not a solution for the costs of buying houses.
https://www.cato.org/blog/folly-bernie-sanders-national-rent...