Re: Couple of questions...

Here is a list of people around the world who will share their kefir grains for free. I got mine from a woman in Derby for just the cost of an envelope, paper wrapping etc. Scroll down past the adverts to the UK list.

http://www.torontoadvisors.com/Kefir/kefir-list.php

According to Dom traditional milk kefir grains can be transferred to a water media to produce water kefir.

I've never made water kefir so don't know the answers to your other questions.