Sunset villas is a community specifically for residents of ages 55 and older. which criteria must the community meet in order to legally enforce this restriction?

The criteria that the community must meet in order to legally enforce this restriction is: At least 80% of the homes must have a resident who is at least 55 years old.
According to the chapter 760 of the housing acts, a community is prohibited from excluding residents based on their race, religions, or gender. BUT, they could choose to create a specialized area for elderly 55 and older as long as the elderly population is 80% or more

What document are you referring to