Why should this exemption be income based?  If a person owns a historic home that is what the exemption is for.  It is not based on how much the home is worth nor how much the person earns, it is based on the fact that the home has a special quality that contributes to the historical knowledge  that we could not get anywhere else and threatens to disappear forever if destroyed.  People that own historical homes should be encouraged to preserve this wonderful sense of history and not looked upon as trying to get away with something no matter how much they earn.   If we cannot as a society encourage history soon there will be nothing left for us to look back on, enjoy and learn from.  Historic homes should be considered special and we should encourage their owners to preserve and maintain them for future generations.  This is worth much more than the dollars that are collected from raising taxes.