What are the tenants of the trailer park afraid of?

More than anything else, they're afraid of being forced to live in the predominantly black neighborhoods of Milwaukee's North Side. Living conditions at the trailer park are pretty horrendous, but the owner has no incentive to make the necessary repairs. He's making an absolute fortune off of the trailer park, and due to a chronic shortage of affordable housing, he's guaranteed a steady stream of tenants. As a result, the people who live at the trailer park are reluctant to make any complaints about the standard of accommodation. If they do, they're likely to be evicted, and then they'd have nowhere to live.
Although in fact, many of the residents come right out and support the trailer park's owner, claiming that he's actually a good landlord. This is an indication of how the trailer park owner has been subtly playing upon the residents' sense of white supremacy to exploit them. He knows that however bad things get at the trailer park, almost no one would be prepared to move into the black neighborhoods on the North Side. So it's better for them to stick with the devil they know than the devil they don't, so to speak.