If you refer to a young person as a whizz-kid, you mean that they have achieved success at a young age because they are very clever and very good at something, especially making money.
[informal]
...a financial whizz kid.
...a whizz-kid physics student.
whizz kid in British English
or whiz kid or wiz kid
noun
informal
a person who is outstandingly successful for his or her age