Planned housing communities, condominiums, and townhomes usually have a homeowners association (HOA). This is a legal entity, which is responsible for the common areas of a housing development.
HOAs are responsible for enforcing the bylaws of the development, which usually requires residents to maintain their property (in the case of a house with a yard, for example).
Where does the money come from?
HOAs collect money from the residents to care for the grounds and the amenities, such as the parking lot, the lawn, and the pool, and are responsible for holding insurance in case something happens to the common grounds and amenities.