Hi Gilbert. Welcome to JustAnswer.com
The only issue that you have using grey water to irrigate with would be someone using non bio dregradeable soaps, detergents or household cleaning solutions. They may cause a health problem and probably kill any plants that you water them with. The biggest offending chemical would be bleach. Not really harmful to humans, but death on a stick for plants.
If you can be sure that this wont happen (or at least not too often) you can use a simple sand filter to prep th e grey water for use irrigating your plants.
As for what kind of plants that is up to you. Any of the native plants will do good.
You can use the water just like the water you use from a faucet, just be sure no one drinks it.
Clearly marking the water lines coming from the grey water filter is a must. Depending on the nationality of your clients will determine the language(s) you must post the signs in. Of course the universal sign of a spigot and a glass with water in it with a big red circle and slash through it is also required (example below).
Please let me know if you have any other immediate concerns.
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