Originally Answered: What's the average salary for a published writer/author?
Authors don't get salaries. They write a book or a sample chapter and outline, submit it, and if a publisher likes it, then maybe it will be published. If the work is published, then the writer will get an advance, and possibly some royalties as well.
Now, you do hear about the really huge advances now and then. However, these advances are only given to well-established authors who are incredibly popular.
Most writers (something like 99 out of 100) need to have another source of income. And most of them take regular jobs, not just for the money, but for things like health insurance and other benefits.
In fact, this is a fact of life for all entertainers. Only a very, very few can make a living from their art. If you go to Hollywood or New York, a great many of the food serving and other low level jobs are done by people who will tell you that they are actually actors. And most musicians have a daytime job, as well. Sure, there are superstars, but for every star, there are 99 burnt out cinders who never made it to stardom.