Usually those are not just vacant but structurally dangerous and beyond repair. That’s about what it takes for the city to actually evict anyone living there in order to condemn a whole block. And again, if you look at where that tends to happen you’d be placing one improved block amidst a blighted neighborhood. It can be a struggle in those cases because, while the buyers intention may be good, they’re usually greeted with hostility by the community. If the program has a time commitment for private purchasers they’ve just tied themselves to a house in an area typically struggling with crime, lack of services, poor school options, and limited resale opportunities for investment. Professional investors face the same hurdles if they buy the whole block, plus typically community protest for attempting to gentrify or change the neighborhood. I did kind of the opposite, purchasing a house in bad condition in an at the time struggling neighborhood which has since improved immensely. We dealt with break ins and thefts, people using our closed yard as a cut through, random people coming to the door demanding that we rent to them because we were somehow listed as a partial HUD rental and hostility from some of the older neighbors because restoring a truly damaged home while living in it is a slow and painful process. We also noticed that once the city sees you as a target for citations they tend to hit you for everything possible adding $100s if not $1000s to the cost of improvement. It makes me feel like as a home owner here I’m being slowly bled while houses that are literally falling down have nothing happen because there’s no money in threatening someone with no money.