Relatives of mine have had dogs for most of their lives. They have been without a canine companion for a few years now and would like another, but they are in their upper 70s with the beginnings of mobility issues.
They have always taken their dogs for walks at least twice daily, but are concerned that this might become increasingly difficult over the next several years. They also have a large, fenced yard with plenty of room for a dog to run. Of course, a fenced yard does not provide the dog with the chance to "get the news of the neighborhood", so to speak. (At least I've been told that this is basically what they're doing when they sniff at things when out on walks.)
They prefer medium-to-large dogs -- golden retrievers, collies, and similarly-sized dogs. (Their dogs are rescues, not purebreds, so treat this as an approximation.) Their dogs live inside the house and get plenty of "people time"; they aren't kept in a yard or barn full-time. If they got a dog they would get one, not two, and would adopt an adult, not a puppy.
How important are walks to a dog's physical and mental well-being? Can a large yard meet a dog's needs?