Use two 1 to many relationships. Three tables total. The table in the middle is usually referred to as a Junction or Helper table.
Table 1 = tblCommunities (Primary Key = CommunityID)
Table 2 = tblHousePlans (Primary Key = HousePlanID)
Business Rule = The same House Plan can exist in different Communitites.
Table 3 = tblHousePlans2Communites (Primary Key = Multi field primary key (CommunityID and HousePlanID))
1 to Many relationship between Tables 1 and 3 (CommunityID to CommunityID
1 to Many relationship between Tables 2 and 3 (HousePlanID to HousePlanID)