Done properly... there isn't a significant amount of money in breeding dogs.
That is - researching various lines - attending shows or working events/competitions to see various dogs/enter your own dogs (this gives you an outside, expert opinion on your dogs abilities/conformation, we all think our own dogs are wonderful of course, we need an outside view too)...
Raising and feeding your dog - travelling to the stud dog - stud fees (price of a puppy usually) - vet fees (breeding related costs are not insured generally) - maintaining a kennel affix costs, annually, you may also need local authority licensing which costs...
Feeding a bitch in-whelp and raising a litter costs a fair bit - you need to have a good 2 to 3K on hand in case you need an emergency C-section during whelping - all the kit puppies need costs - registration costs..
Good breeders do not piss off to work and leave Mum alone, so thats someone home with the dog and then dog and her puppies for a couple of months, not earning..
And yes then theres tax on that income..
Once you calculate all that, there isn't a huge profit.
But if you cut corners of course - no research, use the dog up the road, no showing, no competition, cheap food, no extra vet checks, cross your fingers and spit in your hat that you don't need any emergency vet care, and leave mum alone 9 to 5, 5 days a week... then yes, people do profit.
Really check that they are a good breeder - do they health test? Do they socialise and habituate puppies to typical family life (Smart Pup or Puppy Culture programs for example?), why did they choose the stud dog they used? How has the bitch and dog done in work/competition/showing (after all these dogs must have some attributes that make them worthy of reproducing beyond 'both the same breed'... )...
If answers to those questions are not inspiring... you're taking a massive and expensive gamble. If you are up for a gamble, you may as well gamble and go to a rescue and save a puppy who undoubtedly came from an ill prepared corner cutting breeder just like the one you're swerving... but for a fifth of the price.