RE: keping a dog in a cage?
seth, sounds like to me that your mother is concerned that you will not care for the dog and he will end up spending much of his life in a cage. this would be very cruel.
it is very important to provide any dog a proper facility to be kept in, all dogs should have some sort of house or kennel, whether you decide to use a cage is up to you. some sort of restraint while outside is necessary when no one is home to supervise the dog.
talk to your mother and find out exactly what her concerns are.