You'll need to decide if you'll be breeding for the chicks or flipping the chicks from a hatchery, if you haven't already.
With flipping, you order in sexed pullet chicks from a hatchery and raise them until they're either off heat or POL or somewhere in between. The hatcheries are charging $18-ish for 12 week old started pullets, so that could be the base line depending on your area.
With hatching, there's the breeder flock to maintain and the boys to contend with. With our pure bred chickens we get better than the $18 per, but I also have to feed their parents and brothers.
We went dual purpose and the cockerels grow out until at least 16 weeks. I have more boy space to grow them in than girl space, since the girl's sell on quickly and the boys can barely be given away unless they're bagged for the freezer.
We have the flock now to where I select the girls who will stay as breeding prospects and sell on the rest. Their sale buys the feed for the boys and the parents. We get free dinner at the end of a grow cycle and replacement pullets. I decide on the girls at 12 weeks, 24 weeks and 1 yr. If I have a 2 year old hen, it's because she's the best of what hatched 2 years ago and produces good chicks. If I have a boy past 24 weeks, it's because he's shaping up to be a great rooster prospect.
It isn't a profitable thing to do but breaking even and eating well is way better than nothing. I'm not trying to hustle hatching eggs and straight run chicks, the breeds we have are looking better every generation thanks to the selection process and ample birds to choose from, the cabinet incubator, scald tank, plucker and other tools of the trade have paid for themselves. Any profit to be had gets dumped right back into it in one upgrade or another.
As far as which breed... in flipping go with variety, at least 4 different types. Hatching your own, choose what you like, that you're willing to learn the ins and outs of, that you can do justice for. For example... breeding Marans is trickier than a lot of other breeds, between their physical type, difficulty in gaining quality stock AND egg color to pay attention to... as a breed they need a lot of work to breed correctly and improved on. It can take quite a bit of time to establish a nice breeding flock. Birds that are too rare can be tricky to raise up and get going, as well as finding replacements down the line.
If I see pullet chicks go on sale at the feed store I'll usually buy them. When they're $0.75 or so, I can't make them for that. 8 weeks later they're $15, off heat and ready to go at a cost of about $8.75. Every 2 of them sold is a bag of feed earned.
We chose our breeds based on the table qualities of the boys, so I do Bresse, Marans (in a deep bodied and wide line) as well as some projects/hybrids in other types for more colorful eggs. I'm trying to get to a meatier bird that has girls who lay something neat.