If I were able to visit the person in their home and check out their situation, I may be able to find it do-able. Like someone else said, elderly folks can be in perfect health and able to take care of a puppy just as well as I can. As a breeder, I would think there would be no harm in asking a potential elderly owner if they do have a contingency plan for the pup in the case of the owner's illness or demise.
I would hate to think that as long as I thought I had the ability to care for a dog, someone would deny me one. I do wonder if animal shelters have restrictions..
On the other hand, the reason we have Dreama is because her elderly owner's wife passed away, and he had a stroke and had short term memory loss. He knew he was in constant danger of forgetting he even had a dog, so asked his groomer to take her, which eventually landed Dreama with Dave and I. But if she had been owned by younger folk in perfect health, we may not own her today.