Puss will eat less and no registration fee is involved. Neither do you need to take it for its daily exercise. Cats need care and affection, but they are less demanding and less expensive to keep than dogs. Bear in mind the life span of the animal you are contemplating. Budgies, canaries and cockatoos and so on make interesting pets and can be very responsive to human contact.
Birds are, of course, much happier living in an aviary than in a cage.
Some children may enjoy a decorative tank of fish, or a turtle. All need suitable cage or tank accommodation, and daily feeding and cleaning. Whatever pet you decide upon you are making a commitment. Every year thousands of pets, particularly dogs and cats, are put to death not because they are ill, or old, or because they have done anything wrong, but because the novelty has worn off and they have become inconvenient. Think about it carefully.