I understand how it would work in the case of a developer.  I was just wondering how a normal neighborhood, say a couple of city blocks of normal homes, could put together an HOA and then all of a sudden make anyone that wants to sell or buy a house on that block be required to take part in the HOA.  For example, if they start an HOA in my neighborhood, and I choose to take part in it.  I want to sell my house to someone else.  How in gods name could they REQUIRE the new buyers to be part of the HOA?