The poor would be the first to die. The homeless are all dead after the first Purge. The lower class people have homes and apartments, but that's about it so they wouldn't last long either. Most of the people Purging, most violent criminals and all around violent people, would also die from other Purgers. So with less poverty and less violent people, crime would likely drop. The problem is, who works the stores and restaurants? Who drives the trucks? Who works in the factories? Who makes deliveries? If you cut the lower income population by even 20% we'd be facing huge job issues. The rich would survive the Purge, but they'd soon starve and have no essentials.