There are three residential level. They are level T, TT, and TTT.
Residential T.
The residential level T are the poor people or uneducated people. They live in a cramped space or in small buildings, depending on the size. It is the basis for the city to increase population with fewer resources to be required.
The residential level TT are the people who are educated, and are decent people. Elementary School and Park are required to be built in order to let them move in. They live in decent housing, with some space to spare for residents, also applicable to live in normal, decent homes, some can be applicable for skyscraper apartments. Requirements increased here where commercial lever TT is sometimes required for optimal growth.
The residential level TTT are the privileged of rich people who are very educated. Elementary School, Parks, High School and Sport Facility are required to be built in order to let them move in. They live in a very nice house, can also be in villas, skyscrapers, and penthouses. Requirements are high as it needs high education, other influences, and commercial level TTT for optimal growth.