This is something you certainly should not do if you want to ensure your disabled son has somewhere to live throughout his life. As already said, the house would almost certainly have to be sold on your death. Even if it wasn't, the interest could continue to rack up & the lender would be bound to have a provision in the contract enabling them to sell at a time of their choosing.
If you do raise money now do it in some other way, but you must be very careful because if you die owing money it will be a debt of your estate. The estate will include your house and it would have to be sold to pay the debt if there was no other way to pay it.
It might be worthwhile you putting the house into a trust. I don't know whether this is feasible - you need specialist advice from a solicitor who is a member of STEP (google it). It will cost you, but could well avoid serious consequences down the line.