I know it seems like a good option, but a dog farm (they are called puppies in my world) are terrible ideas. Listen to why, and I will suggest some ways how your love of dogs can become an honorable and profitable business.
What makes dogs so wonderful is their ability to connect with people. We humans are limited in the number of connections we can make with dogs. After two or three dogs, it will be difficult for most people to give enough time and training to the dogs. Untrained dogs are destructive: they flee, they bite humans, they dig up the land, they chew the house. People who “grow” dogs bring them into cages.
If you put a dog in a cage, it will be unfortunate. The way the workers / owners of the puppy mills handle it is a human trick called “rejection”. People pretend it’s okay, they do not care if the dog suffers, and they do not feel so bad when they lock up the dog.
If you are not interested in the animal’s experience, why should you? The answer is money. And if the whole purpose is money (and suffering is denied), the more dogs I can put in my room, the more money I can make. It’s a slippery slope that ends with dogs in cages that are so small they can not turn, stacked so that the feces and urine of the tallest cages fall on the animals below them.
Hell is preparing a room for people who do this with dogs. Good people devote their lives to closing these places.
Then there is the economy of energy: agriculture is best powered by plants: they provide seed, soil and water and they grow with solar energy. The next best farming is with domesticated animals and vegetarians who happily live in groups such as cattle or chickens. Again, you provide for land and water. Ideally, animals can eat the vegetation on their land or be supplemented with grass (hay) or grain. The higher the food chain, the more expensive the feeding dogs, whose feeding is very expensive.
Another problem with breeding dogs is that dogs work quite well if they are not supervised. There are millions of stray dogs in America, maybe this applies to you too. In America, the surplus of dogs is so great that shelters kill thousands of them every week. Many people believe that it is unethical to increase the dog population.