Reverend Sykes is definitely a respected leader in the black community, so he would be their go-to-guy with any of their concerns. Also, with him leading church every Sunday, he is the source of information about those who are sick, afflicted, or sinners. During his Sunday sermon which Jem and Scout attend, Reverend Sykes calls the sinners to repentance, but this also gives the reader a look into the types of lives his flock is living.
"His sermon was a forthright denunciation of sin, . . . he warned his flock against the evils of heady brews, gambling, and strange women. Bootleggers caused enough trouble in the Quarters, but women were worse" (122).
It would seem that the Reverend's concerns around their black community deals with drinking, gambling, and casual relationships with women. He even goes on to call individuals out on their sins as follows:
"Jim Hardy had been absent from church five Sundays and he wasn't sick; Constance Jackson had better watch her ways--she was in grave danger for quarreling with her neighbors; she had erected the only spite fence in the history of the Quarters" (122).
It would almost seem like the Reverend had become a little bit of a gossip, but his warning calls certainly give insight into how the community is interacting with each other and what vices they struggle with. On a more sober note, though, it is interesting that it was so difficult for the Reverend to collect $10.00 for Helen Robinson. Reverend Sykes doesn't dismiss the congregation until they have collected money enough to help Helen. There are a couple of reasons why it is difficult to raise the money: either the community dismisses her because of her husband's trouble and they don't want to help, or the community is just so poor that they can barely sustain themselves let alone help a local family in trouble. The second is more likely the situation due to fact that they are in the middle of The Great Depression. But Calpurnia does answer Scout when the question is asked why Helen can't get work:
"It's because of what folks say Tom's done, . . . Folks aren't anxious to--to have anything to do with any of his family" (123).
The worst case scenario is that the black community would shun one of their own during a time of crisis. The allegations against Tom Robinson are deeply insulting and no one wants to be associated with helping out the family of a possible rapist. Based on the support the community gives Tom on his day in court, though, it's probably more likely that Helen couldn't get work because white people don't want to hire her, not because black people won't. Again, the black community is probably just too poor to be able to donate more than what Reverend Sykes asks for.