Congrats on selling a book! You’ll receive an advance, but it's paid in installments over time. Advances are based on estimated sales and can influence marketing efforts. Typically, they’re split into payments at signing, manuscript delivery, and publication. For example, a $100,000 advance could be split into three $33,333 payments. Authors typically don’t repay advances unless they breach contracts. Many factors affect payment timing, taxes reduce net income, and not all books earn out their advances. Ultimately, while advances seem substantial, they likely won't replace your day job income yet.
https://www.literatureandlatte.com/blog/how-book-advances-are-paid-to-authors