Sooner or later, every professional writer is approached about working for free. This might not seem like something anyone would want to do, but it’s a very familiar situation for writers. For example, when you’re writing your first novel, possibly at the weekend or in the evenings if you have a job in the real world, no one is paying you for that work. If a publisher accepts your manuscript for publication, you might receive some kind of advance but any work to revise the book and complete any edits will all be on your own time.
Of course, you’re hoping that the book will eventually sell some copies. Even if you don’t sell millions, you might at least attract enough buyers to convince you that you’ve not worked so hard for nothing. However, you’re still not getting paid while you write the book. Children’s authors have the opportunity to be paid for vising schools and talk about their work, but the initial creative period all transpires in your own time and with no financial rewards.
Even if you’re an established writer, every novel isn’t paid work while your writing it, but there’s hopefully income later. This is a situation faced by many self-employed people all the time, whether they’re plumbers, electricians, painters, and numerous other professions. They might receive a deposit from their client as an act of good faith, somewhat like a writer’s advance, but the bulk of the fee isn’t paid until the work is completed.