First, the key is when you closed on the FHA loan. Guidelines for flipping a house indicate that the buyer of the home has to hold it for 90 days from the time the deed was recorded before it can be sold and a new buyer can close a new FHA loan. If the house has been deeded to the buyer that closed at $80,000 for more than 90 days, then becoming a seller, you need to carefully read your loan documents to see if there is any hinderances to paying off the FHA loan. Typically you should be able to sell it by having a buyer that will use a conventional loan prior to the 90 day requirement from FHA. As to the housesitting buyer, unless you have a written option to buy or a written agreement, that spells out terms, the seller can cancel or you can cancel. However, you should consult an attorney as there are circumstances unknown to give a specific answer to this question, my answer is generall in nature as a Realtor but this question may require legal advice.