This happened to us when the buyer of our house claimed with only days to go to closing that she 'didn't know' about the need for a 10% deposit - she was buying our house with the proceeds of her own, wasn't getting a mortgage and therefore assumed that a deposit didn't apply - idiotic, I know, but that was her excuse. We had a sleepless night before deciding to go with her - if we'd insisted on her getting bridging or another type of loan at that stage we'd have been in danger of losing our new place. It all worked out okay in the end but our hearts were in our mouths - basically WE paid a 10% deposit for our new place so if things had gone wrong we'd have lost everything. We spoke to our buyer and she assured us that she was ready to go ahead - but we were saying rosaries that she'd remain hale and hearty for the duration of the sale process!! I wouldn't recommend it as a route to go down if you have any other option but we didn't, at the time.