If you are set on breeding, remember that you may well not even break even on costs.
You need to get the required health tests done, and only breed if scores are good. You have to pay for these. You will also have to pay stud fees, and all associated travel. (COI tool is free on KC website, so it's easy to check whether your proposed mating is a good match - potential puppies COI should be same as or lower than breed average, and ideally lower than that of the parents)
Check what your insurance covers - routine costs of normal pregnancy won't be (so additional food and wormers from day 40 onwards not covered) and costs of complications of a pregnancy are only covered in the more expensive policies. If yours doesn't cover that, check you have the ability to pay for OOH vet and caesarian section as minimum contingency fund.
Then of course you have all to costs (time and money) of the litter - everything from whelping pen in a good place, through dealing with pee everywhere, general chaos, more food, more bowls, vet checks, jabs, any medical attention they need, microchipping, KC paperwork, toys, early socialisation, time and effort of vetting potential purchasers and puppy contracts (the list could go on and on). And of course what would you do if a puppy didn't sell (not enough buyers, medical issue) And how you would cope with returned puppies - all good breeders require that puppies be returned to them if any need for rehoming emerges (you don't usually need to refund; you do need to take the dog back)
Have you got an experienced breeder who will help you? It's really important you know about signs of labour in bitches and when to call for help. Have you checked your vets OOH provision?