Landlords want to make money, and as the parent pointed out, low income housing is clearly not a priority in the area.
What's your explanation for that behavior, if not racism? You might argue it's because their white customers would retaliate by not patronizing their business. But that just proves that businesses will discriminate based on race, even if it's not due to the owner's racism but their white customers'.
For example, seeing a family of any race with obvious signs of poverty (large family size, rundown vehicle or none at all, shabby clothes, etc) and not wanting them to move in would be classist. But assuming a black family is poor because they don't have obvious signs of prosperity (very nice car of the right brand, very nice clothes that aren't loud, few and well-behaved children, etc) is racist if the same class heuristics aren't used to determine if an asian family isn't poor.
Although classism is its own problem, it's also very often just a more palatable presentation of racism. In particular, if your baseline class assumption about various races is different and you don't want to associate with people below a certain class, the effect will be racism.
I'm honestly baffled that anytime someone on HN brings up racism in the US it's immediately countered with: "It's about class, not race." There's ample history in Jim Crow laws that white Americans discriminated explicitly by race. Specific to the region mentioned by the grandparent, Washington, DC, like much of the South, had racial covenants that made it illegal for African Americans to live in much of the city.
Of course there has been, and continues to be, very real discrimination by class. But we know that legal discrimination by race in the US existed well into living memory. Why would we immediately assume that it has stopped?
https://wamu.org/story/14/01/17/how_racial_covenants_shaped_...
plenty of white people in the bay area that can't afford housing.