Re: I don't dream about these things
There are only two circumstances I know of where an author will have to pay back an advance, and neither applies to a first time writer who has actually written a novel and had it accepted by a publisher.
After your first novel, you will usually receive a contract and an advance before you write the next novel, said advance being loosely based in size on how well the first novel sold, and given because you've written an acceptable synopsis/outline and/or sample chapters. In other words, you get the next advance before the novel is actually written.
If, for whatever reason, you fail to finish the second novel, the publisher can ask for the advance to be returned. Or, if you do finish the second novel, and the publisher decides it's unacceptable, the publisher can also ask for the advance to be returned.
It should also be pointed out that advances are almost never paid in one lump sum. A first time writer who has actually written and sold a novel will usually receive half the advance on signing the contract, and the other half on publication, and there can be almost two years between these events.
I receive my advances in three parts; one third on signing the contract, one third on delivery and acceptance of the novel itself, and one third on publication. Royalties are then paid twice a year.
But advances can be broken into many parts. I know one writer who received a very large advance, and it was broken into twelve parts, each part paid monthly. I know another who received a fairly large advance, and had it paid over three fiscal years. This gave him enough money to live on, and kept him in a lower tax bracket. He asked the publisher to pay out tyhe advance this way, and the publisher obliged.
Anyway, whatever the size of the advance, you likely won't receive it all at once.