Dog-sitting? would you do it?

the kid who mows for me got a puppy. he went to FL. comes back and tells me his pup nips. Decides to trot off another weekend and wants me to watch dog. My dog is old and falls. She licks other dogs ears (another dog had to go to vet for ear infection). Would you even watch a dog if the animals have not been socialized? if you think the kid should take responsibility and bond/train with his animal to make them life-long companions? I felt bad. but knew it was not a good situation for me. it’s hard for me to say no.