All biographies record that Sanders earned a living between graduating college and running for Mayor of Burlington at age 39. Wikipedia is typical, and gives references.
> After graduating from college, Sanders initially worked in New York City in a variety of jobs, including Head Start teacher, psychiatric aide and carpenter. In 1968 Sanders moved to Vermont because he had been "captivated by rural life." After his arrival there he worked as a carpenter, filmmaker and writer.
and
> Sanders worked as a writer and the director of the nonprofit American People's Historical Society
Nowhere does it say that he was not paid for these jobs.
**Claim is false.**