You may want to explain that in order to have a no or low maintenance tank requires the tank to be extremely balanced in respect to stocking, water chemistry, and ecological soundness and this all adds up to a lot of money on the front end and usually ends up with a rather boring looking tank( unless it is a rather large tank.) In the long run, it is better for the fish,( IMO
) to do some routine maintenance than none at all.
, it's better he not set up a tank at all than set up one that will only be a poor environment for the fish to live in.
The reality is that not everyone is a good fit to own a fish tank. Better they know up front than in the end.
Hope this helps