My major concerns would be:
Providing enough exercise and mental stimulation. Welsh Springer Spaniels MUST have regular opportunities to vent their energy and do interesting things. Otherwise they will become rambunctious and bored -- which they usually express by barking and destructive chewing. Bored Welsh Springers can make a shambles of your house and yard.
If you simply want a pet for your family, and don't have the time or inclination to take your dog running or hiking or biking or swimming, or to get involved in hunting, or tracking, or agility (obstacle course), or advanced obedience, or a similar canine activity, I do not recommend this breed. Trying to suppress their desire to run and work, without providing alternate outlets for their energy, can be difficult.
Separation anxiety. More than most other breeds, Welsh Springer Spaniels need a great deal of companionship and do not like being left alone for more than a few hours. They tend to express their unhappiness through destructive chewing and barking. If you work all day, this is not the breed for you.
Providing enough socialization. Standoffish by nature, Welsh Springer Spaniels need extensive exposure to people and to unusual sights and sounds. Otherwise their natural caution can become shyness, which is very difficult to live with.
Teaching your Welsh Springer how to be confident with the world is essential. Learn how to socialize your dog on my Welsh Springer Spaniel Training Page.
Grooming. To keep their silky coat free of mats, Welsh Springer Spaniels require regular brushing, and also trimming every few months.
Shedding. Welsh Springer Spaniels shed quite a bit. Their hairs come off on your hands when you pet them, stick to your upholstery and clothing, and hide under the furniture. You'll need to vacuum frequently.
Health problems. Seizures and epilepsy are the major problems, along with hip and eye disorders.
