Agree that Piha is not really realistic for commuting to town. Also if you live in Piha you will be on tank water (roof collected) and have a septic tank, etc..
I live in Titirangi and it is a wonderful and affordable suburb (and you can actually find flat sections between all the steep ones) + the water out of the tap is collected in the waitakeres which makes it very nice and soft and with a surprisingly low TDS which means it is just great for all my south american cichlids.