Hi there, It really depends on where you are, you should research what regulations are in your area, some areas even forbid the breeding of livestock for sale. There's very little profit in chicken breeding unless you really know what you're doing, and those breeders that are making money, have spent decades and loads of resources perfecting their lines and genetics.
Choose a breed, buy from a reputable breeder, ( you can find breeders clubs online) breed according to the breed standards (the APA) to set your stock out from other local breeders or hatcheries who will be cheaper.
Getting npip certified wouldn't hurt.
Have you fully considered everything that's going to go into this? somethings look good in theory but in execution, are a rats nest. Some things to consider:
Are you prepared to lose money for the first 5 years or so until the quality of your stock is worth buying?
Feed prices, coop maintenance. Do you have the room? At least 4sq feet per chicken in the coop, at least 8sqf in the run per chicken. Some areas limit how many outbuildings or chickens you can have. The time and energy? Vacations and sick days are hard to do with livestock. Are you allowed roosters? Hens are noisey too. Are you prepared to dispatch birds, like extra cockerels you'll end up with or birds that don't meet the standard? Do you have money set aside for vet bills if necessary?
Does your area limit how many chickens you can have? What kind of predators do you have in your area that you'll have to work against.
Will you use an incubator or broody hens? Do you know how to euthanize chicks that hatch but are sadly deformed or dying? It's unfortunate but there are many strings attached to chicken keeping in general, nevermind breeding. I'm really, truly, not trying to scare you or talk you out of it but breeding any animals 'for business' has loads of strings attached. Chicken breeds go through fads, you could spend years perfecting a good line of a certain breed and by that time, few want them since the newest hot trend in chickens is something else. 5 years ago here, easter eggers were the best things since potato chips and now...people sell pol pullets for $10-$20, hardly breaking even on feed costs. It's rough.