A guard dog can be a welcome addition to a home and can provide a sense of security for homeowners. With this said, trained guard dogs do not come cheap. To purchase a fully-trained guard dog, a budget of up to $10,000 is required. If training a dog from puppyhood to become a guard dog is more your thing, this can be done for a relatively low cost, but requires a great deal of time spent on training. To help the process along, dog owners may wish to attend dog training classes, which cost on average, $75 per session.