Best greywater system

Just building a new house. Wondering what would be the best way to treat greywater and rent use it in the garden?

The simplest way is to not treat it, just use it as is to water trees, bushes, etc.  Subsurface systems are best for avoiding contact with the grey water.

If you must treat it, then a constructed wetlands is probably the best bet.  The output of a well designed constructed wetland is no longer grey water, but it's not exactly pure water either.

However, they don't tend to work very well during the winter in cold climates (if that is an issue).  

The most important thing is that the plumbing is high enough that you get enough slope. The really simplest thing is a hose which can be moved around in the garden. The wetland is good too but most plants are dormant in winter.