No. The communities usually have a 80/20 ratio because it would be discriminating to not all housing that is on the open market. However, there are ways to have the homes less appealing to families with children. Covenants typically disallow swing sets, kiddie pools, basket ball hoops and such.
Also, some neighborhoods have an older population based on the density the City allows. Some concessions are granted to developers who build for over 62.