You can't back out if you have a signed written contract, whether it is FSBO or otherwise: once the contract is signed, the seller is obligated to go through with the sale. Your financial issues are wholly irrelevant; one party's personal financial difficulties are NOT legal grounds to terminate the contract.The buyer could sue for breach of contract if you try to not go through with the transaction. At a minimum, they could get financial compensation--e.g. for any costs they incurred as part of the transaction (loan origination fee for a mortgage; legal fees if they hired a lawyer to help; costs for any inspection(s), etc.) or due to it falling through (e.g. "carrying costs," such as rent and/or storage costs for the additional time they have to rent a place to live or store their belongings because this sale falls through, until they can find and buy a new place; etc.). More significantly, they may be able to get "specific performance" in a lawsuit; that is, they may be able to get a court order requiring you to go through with the sale and sell the home to them, on pain or under threat of "contempt of court" for ignoring a court order. That is, if they sue you and get specific performance and you still don't sell to them, you could be jailed for contempt of court if you violate the court order.