Which piano keyboard for a 5 year old?

[ItWillAllBeOkayInTheEnd]

I am completely unmusical, but DD(5) is going to learn piano at school. Which keyboard should I get her for at home? Can you buy them second hand? Presumably she'll outgrow it in a couple of years, so I don't want to spend too much.

You don't outgrow a keyboard If she is learning the piano, get one that doesn't do any effects or imitates other instruments but has keys the same size as a standard piano. Don't get a keyboard with weighted keys as their 'touch' is very heavy and completely different than that of a piano.