The Radley family, as a whole, was not poor. Having said that, they also were not rich. They, like the Finches, were average, middle-class residents of Maycomb County, but their property appeared downtrodden because of Boo Radley's social reputation, among other factors.
Poor families in Maycomb County include others like the Cunninghams and the Ewells. In the case of the Ewells, local authorities overlook their legal transgressions due to the family's poor nature, including their drunken father.
Cunninghams, however, are "poor but proud:" While they may be lacking in money, they do not readily accept charity from the community or others, as demonstrated by Walter's refusal to accept a quarter for his lunch from Miss Fisher, Scout's first grade teacher.
Boo Radley was not poor financially speaking. He was, however, poor in relationships. He was kept away from everybody first by his father and then by his brother. He was involved with a prank when he was a teenager and placed under "house arrest" by his father. After his father passed away, his brother took over. He is a very misunderstood character who is feared by many. They, including Jem and Scout, fear him because they do not know anything about him. At the end of the novel, he is proven to be a very gentle and caring person.