Who is Raymond Sintes and what is the word around the neighborhood regarding Raymond?

Raymond Sintes is a foil to Meursault. This means that he provides a contrast to the protagonist, emphasizing certain characteristics of his. If Meursault is amoral, his neighbor Sintes is completely immoral. He's a pretty unpleasant character, to put it mildly. He is a macho chauvinist who physically abuses his mistress and generally treats her like dirt. It is Sintes's contempt for his mistress that leads to Meursault becoming embroiled in a scheme that ultimately ends in murder. Sintes is devious and manipulative and thus is able to get Meursault to do his bidding.
The reputation that Sintes has in the neighborhood is that of a pimp. And he certainly gives the impression of being one, with his flashy clothes and his reputation of violence towards women. Sintes is indeed subsequently exposed as a pimp in court, but he remains somewhat cagey about what he does for a living. Despite everything, Sintes still seems keen to maintain a certain reputation in the neighborhood.