Overall the English Cocker Spaniel is a healthy breed that lives 12 to 16 years. There is ample documentation on the health and health testing and I would strongly suggest if you are interested in the breed to become familiar with the issues. The key areas of health are OFA, Patellas, CERF, Thyroid, and the diseases that now have genetic testing available: PRA, FN, and AN.
As well as overall health, grooming is an important aspect of the breed. At a minimum, the ECS should be brushed daily to ensure the dog remains mat free. As well, proper brushing cleans the fur of dirt and dander and helps distribute the oils. It also aids in bonding with your dog and most truly enjoy this time.
As well as dailing brushing, their dental health is also important. Daily brushing is necessary to avoid plaque buildup and staining.
The nails, at a minimum should be trimmed weekly. If the nails grow too long, it not only becomes uncomfortable for your dog to walk, they can catch on objects and become damaged and painful. If your dog has dew claws, pay particular attention as these can curl around and cause pain.
Links to learn more about the breed: