HI Michelle, I am not sure if i interpreted your question correctly. Do you mean an expected answer from a 6 year old child?
If this is what you meant, I think it depends a lot on the child's understanding of a profession and why grown ups have to work. At the age of 6, i am quite sure he could understand. But the question is what kind of profession are you referring to? An example could be that the child may have gotten the idea from media ,e.g the television, about superheroes, and may want to grow up to be one himself!
I am not 100% sure if i answer your question but do elaborate more if i didn't