Vacant housing for sale and vacant housing for rent, respectively.
These are nationwide trends, to say nothing of supply issues on a metro by metro basis. The fundamental issue with housing today is the lack of supply. This leads to higher prices locally and nationally. Then due to zoning, the areas with the highest "demand" (thus, prices) you can't build new housing, pushing people in to where locally cheaper housing is located (where you can't really build that much more new housing of, again) causing displacement and gentrification. Repeat down the economic ladder until you put people on the street.
Anything less than more supply is putting a bandaid on a bullet wound. Will vouchers help? Maybe! But all it does it temporarily dampen the impact that low supply causes. Inevitably you must build more housing and that can only be done in a sustainable and affordable way by relaxing zoning laws in dense areas with good job and transit access.
Vouchers for now, zoning for the long term to actually fix the issue.