What does it take?
Hopefully the defining factor is not employment.
If to 'do science' is simply to execute the scientific method then one can be said to be a scientist (a practitioner of science) only if and when one is executing it. That doesn't need any credentials or career, and through this strict lens the scientist by profession only earns their title during practice.
I personally take a more broad definition of scientist than this that can include people not currently 'doing science' and also laypeople.