Undecided Question

Help with an old dog with alot of health problems?

My sister owns a toy poodle and hes 13 years old. My sister left the dog at my parent's and my house because she works too much to be able to look after him in her apartment. This dog is a complete mess! His teeth are rotting and causing a terrible smell. The smell is so bad that you can't pet him and he stinks up any room he walks into. His ears appear to be rotting off! They are full of scabs and have lost hair. He also is constantly developing hot spots and licks his skin raw.

I have told my sister to take him to the vet, but she never does. My parents and I don't have money to take him either. I feel bad for him because I think he is suffering and I try to do what I can to take care of him.

Does anyone have any advice how to treat what is wrong with him, or is it just old age? Should he be euthanized because he is suffering?