In my place there is a kennel where there are atleast 10-15 labs. The owner use to walk them daily two times. The dogs have play mates (other dogs), his dogs are very good at health, temperment. So I believe If u have time to devote, them only open a kennel otherwise don't ruin dog's life.
One of the best advantage of kennel is that you have a pack from which u can learn a lot practically as compared to what you learn from internet and books. Hope this info helps u..