Doesn't sound exceptional to me. Most of the authors I have some personal knowledge of manage through exactly that: spouses, grants, book sales, residencies and teaching creative writing.
Compared to the postal workers, accountants and insurance agents named in this article they can count as exceptions too, save for the creative writing teachers.
I think Don DeLillo quit his job before his first book and never looked back.
I think Don DeLillo quit his job before his first book and never looked back.