Show all rows from table parcels, and only those from the other two tables that match the join criteria (the order makes a difference):
SELECT parcels.*, areas.code, areas.desc, owneralts.owner AS altowner, owneralts.address as altaddress, owneralts.city as altcity, owneralts.state as altstate, owneralts.zip as altzip, owneralts.phone as altphone, owneralts.comments as altcomments FROM owneralts RIGHT JOIN areas RIGHT JOIN parcels ON areas.id=parcels.area ON owneralts.owner_id=parcels.alternate_owner_id WHERE 1;