Cat with kidneys that don't work properly

So I've been considering adopting a cat whos kidneys don't work properly. he isn't in kidney failure, his kidneys just don't function properly. aside from having plenty of running water, special food, and annual vet visits to ensure he's still healthy what can I do to make sure he stays healthy? are there specific things I should do to make sure he stays healthy?

he's a Russian blue mix that's less than 1 year old and I love him so much.