Young animals require lots of work, which can include:
Hourly feedings of a special puppy/kitten formula with a dropper or a bottle until the pet will lap from a bowl
Stimulation for urination and defecation (this can be done by dampening a cotton swab with warm water and rubbing their bottoms with the swab)
Intense housetraining or litter box training
Specialized healthcare and disease prevention
Depending on the flexibility of your schedule it may be more appropriate for you to foster animals older than four months old. Many of these animals cannot be left alone for more than four hours at a time. At eight weeks old, the kitten or puppy is old enough to be spayed or neutered and should be returned to the shelter for adoption.