Low-income residents, slums, and squatter settlements are typically found in what is often referred to as the "informal" or "peripheral" zones of urban areas. These zones are characterized by inadequate housing, limited access to basic services, and higher levels of poverty.
In urban planning models, such as the concentric zone model by Ernest Burgess, low-income populations often reside in the outer zones of a city, where they might occupy informal settlements. These areas are commonly near industrial zones or on the outskirts of urban centers where land is available and often cheaper, although they may not have the same infrastructure and services as more affluent neighborhoods.
Informal settlements can occur in various contexts around the world, often as a result of rapid urbanization, migration, and insufficient housing policies.