https://www.huduser.gov/portal/usps/index.html

This data seems to be available to non-profits and gov. I'm neither, but also not looking to profit from this data.

It looks like there's a ton of businesses selling this dataset and similar sets for real estate business, but I'd rather get it directly from the government for free if possible.

Any ideas? Really I'm interested in any datasets about vacant properties in the US, preferably cities.