Agreed, you should never ever impulse buy any animal, much less a delicate animal that needs a carefully regulated environment and can live well into its 20s. Especially if it’s supposed to be for a child that has already lost interest in a previously purchase pet. I have half a dozen leopard geckos that are 19 years old and aren’t slowing down much, I hope you’re prepared to do a lot of research in a very short time.
edit: check out this link for a post with a bunch of additional care sheet links: