In the social hierarchies of the Aztec and Inca, which group was expected to support the upper class with their labor?

In Aztec social hierarchy, people who are called "Serfs" are the ones expected to support the upper class. They belong to the lowest social class in the Aztec culture and required to do labors for the nobles. As for the Incas, "Commoners" (farmers, artisans, servants, etc.) are required to support the higher class for they do not practice slavery. Majority of Inca's population belongs to the commoner class.