Help me put my old dog to rest

I am seventy years old and have a dog who is twenty years old. He is mostly blind and totally deaf. Up until a couple of weeks ago he was reasonably cheerful, walking up the road everyday - but now he is increasingly confused and distressed. He does not want to walk anymore. One of his back legs is almost totally useless. I would have taken him to vet to be euthanised, days ago, but am at the moment, almost broke.