I heard about this about a friend who was selling their apartment in London. Every sale is conditional on the sale of another house and eventually her sale didn't go through as they was a break in the chain. That's like so stressful, especially if the money is need for urgent matters.

Australia is so different, very few home sales are conditional to the sale of your current place. At the numerous auctions here, the sale is unconditional, unless the terms are pre-agreed prior to the auction. Don't think there is a 3 day cooling period applicable for auctions, or for private sales.