Hi Greg,
Im not sure its possible to have 0 kh and gh out of the tap.. maybe theres something wrong with your test kits.. and if true you would see pH fall very fast.
Using baking soda is a quick fix.. definitely not long term. It causes alot of pH swings if you are not careful. I have a very low KH here and when I want to buffer my water and add some minerals I use crushed coral or oyster shells (much cheaper from a poultry supply house) in a nylon stocking. I do this regularly here for my fry grow out tanks.It works great and lasts forever.
Hth,
AL