I think maybe reading this book
http://permaculture.org.au/2008/09/18/humanure-handbook-free-download/Gives a good fundament/knowledge to make a decision on the matter
There are lots off diferente aproaches, DIY models on the nett.
I have built, a greywater and blackwater system my self, to get it approved I had to document every step give references to studys (free as well) and finaly deliver test samples of soil or ground water on request.
The ready made (plug and play) systems are expensive do to certification/dokuments/low turn over.
Quite easy to build low tech if you have a plan and the tools.
My best advice is build a gravatie fed one, so you are not deepended on eleectriciety and the instalations/wiering that comes whit that.
