Given his medical history it is very unlikely (which is one of the reasons I reckon he should take himself on a round-the-world cruise, etc.) but you never know!
We have a good deposit so the LTV is low and the mortgage repayment will be small. Our circumstances would have to change drastically for it to affect us. Of course they could change drastically and we could lose our shirts, but we would have to accept that with any investment. At least if we go bust and the house is auctioned his right of residence can't be touched so he would be relatively secure.
The house is in good shape, we look after that already.