There's always going to be a need for physically demanding jobs require some level of skill, and it doesn't take a very high IQ to do those jobs. Where lower IQ people tend to have problems is abstract thinking. Such a person might be perfectly capable of doing math required for their work because they do it over and over without having to apply the concepts to new things, even if they would never understand it in a more theoretical context. The problem is those jobs will always have shitty pay as long as we have hordes pouring across the Rio Grande looking for a handout.