Lots of good advice here already! 
It's a labor of LOVE and not a get rich EVER scheme..
Sell popular breeds... not rare breeds is my experience.
I hatch and sell chicks for $9 each straight run. $8 each if you buy more than 4. This is higher than anybody else on Craigslist. And I'm remote so most people drive not less than 90 minutes each way. I offer to take back males for free as a community service with the understanding they will become food for my family or pets or someone else's and not returned to my flock. So far, not a single male has been returned.
BUT... I'm not selling hatchery birds. I'm selling birds that have been gathered from different breeders, and I select for quality and cull for faults in my parent stock. And make that clear in my ad. People WILL pay for quality... sometimes. I grow out as many birds as I can for myself and sell of the extra pullets each year for $15-30 each depending on age and lay point. We eat the extra boys, even Silkies. Yes, there is competition because lots of people grow out a bunch of hatchery chicks and sell them off as pullets and such... BUT it's not REALLY competition... because I KNOW I have a good product. And so do my previous customers... MANY are repeats.
The funds I have invested in fencing and housing and my original stock will NEVER be recouped. But I do this for ME... and sharing and having SOME of my cost covered is just a bonus.
I did sell a batch of mix breed chicks that I had in the incubator (I have 3, lets not talk real cost) to test it early in the season, by replying to someone else's ad who wanted "cheap" chicks. I let them go for $2 each within a few days after hatch, the people were very happy and reported back even sent me pics! Again, it isn't JUST the chicks I am selling. It's also me. I'm selling my personality and dedication in addition to my knowledge and willingness to be there if they have questions. This ALL comes across in any coversation had with buyers.
I don't let any of my chicks go usually until 5-7 days old because early mortality is a reality, and I don't want anyone to have chicks dying. The cost of heat and bedding and feed add up the longer they stay.
I'm not NPIP certified so that limits me to pick up and local delivery. No shipping. But all that would be an added expense AND chore for me that I'm not interested in.
There could be challenges with illness or predators. In my case, one of my specialty breeds is (bearded) Silkies, so I have to deal with broodiness. Actually I deal with that in my Marans as well. And accidents happen.. I just lost my head rooster, so no more hatching that breed until my grow outs are mature.
My final answer, though I'm sure I have lots more information to share (gotta go tend the flock quickly).. is NO it isn't profitable. But yes you CAN cover some of your expenses and have a TON of fun (and labor) doing so. I need to make at least $100/month JUST to cover my feed bill (OK it MIGHT cover incubation power). Well, that would be nice... but I do this for me. So the cost is offset by not having to go to the gym or therapy and a general sense of well being.
Since January.. I sold $500 worth of chicks. And $140 worth of pullets and ONE cockerel. With only 2 (maybe 3) ads placed in CL. I find placing the add and letting it sit gets better response than renewing every 2 days, that makes you look desperate. It always takes a couple weeks to get truly good response.
I have gone through a LOT of breeds... it must be a breed that you love having or it won't be worth it. Not all breeds are as good in reality as they seem on paper. For me... I wouldn't do Orpington. Good bird, but heavy on the feed bill and too readily available. Maybe Lav or Jubilee. But I think it's a lot about the breed. Know your market and know yourself. I haven't yet decided where I will price my white faced black Spanish or my Speckled Sussex since I don't expect either breed to sell as well as the Marans and Silkies and people can buy sexed chicks all day long at the feed store for under $4 each. And next year I will hopefully have bantam Ameraucana. But the projects and upgrades never seem to end. In chicken math.. we try not to talk REAL numbers!
But when I see others selling straight run chicks for $5 each... my thought most often is... meh, I can get that from the hatchery and not have to deal with someone else's possible parasites or disease for less $.
Good luck!

It's a labor of LOVE and not a get rich EVER scheme..

Sell popular breeds... not rare breeds is my experience.
I hatch and sell chicks for $9 each straight run. $8 each if you buy more than 4. This is higher than anybody else on Craigslist. And I'm remote so most people drive not less than 90 minutes each way. I offer to take back males for free as a community service with the understanding they will become food for my family or pets or someone else's and not returned to my flock. So far, not a single male has been returned.
BUT... I'm not selling hatchery birds. I'm selling birds that have been gathered from different breeders, and I select for quality and cull for faults in my parent stock. And make that clear in my ad. People WILL pay for quality... sometimes. I grow out as many birds as I can for myself and sell of the extra pullets each year for $15-30 each depending on age and lay point. We eat the extra boys, even Silkies. Yes, there is competition because lots of people grow out a bunch of hatchery chicks and sell them off as pullets and such... BUT it's not REALLY competition... because I KNOW I have a good product. And so do my previous customers... MANY are repeats.
The funds I have invested in fencing and housing and my original stock will NEVER be recouped. But I do this for ME... and sharing and having SOME of my cost covered is just a bonus.

I did sell a batch of mix breed chicks that I had in the incubator (I have 3, lets not talk real cost) to test it early in the season, by replying to someone else's ad who wanted "cheap" chicks. I let them go for $2 each within a few days after hatch, the people were very happy and reported back even sent me pics! Again, it isn't JUST the chicks I am selling. It's also me. I'm selling my personality and dedication in addition to my knowledge and willingness to be there if they have questions. This ALL comes across in any coversation had with buyers.
I don't let any of my chicks go usually until 5-7 days old because early mortality is a reality, and I don't want anyone to have chicks dying. The cost of heat and bedding and feed add up the longer they stay.
I'm not NPIP certified so that limits me to pick up and local delivery. No shipping. But all that would be an added expense AND chore for me that I'm not interested in.
There could be challenges with illness or predators. In my case, one of my specialty breeds is (bearded) Silkies, so I have to deal with broodiness. Actually I deal with that in my Marans as well. And accidents happen.. I just lost my head rooster, so no more hatching that breed until my grow outs are mature.
My final answer, though I'm sure I have lots more information to share (gotta go tend the flock quickly).. is NO it isn't profitable. But yes you CAN cover some of your expenses and have a TON of fun (and labor) doing so. I need to make at least $100/month JUST to cover my feed bill (OK it MIGHT cover incubation power). Well, that would be nice... but I do this for me. So the cost is offset by not having to go to the gym or therapy and a general sense of well being.
Since January.. I sold $500 worth of chicks. And $140 worth of pullets and ONE cockerel. With only 2 (maybe 3) ads placed in CL. I find placing the add and letting it sit gets better response than renewing every 2 days, that makes you look desperate. It always takes a couple weeks to get truly good response.
I have gone through a LOT of breeds... it must be a breed that you love having or it won't be worth it. Not all breeds are as good in reality as they seem on paper. For me... I wouldn't do Orpington. Good bird, but heavy on the feed bill and too readily available. Maybe Lav or Jubilee. But I think it's a lot about the breed. Know your market and know yourself. I haven't yet decided where I will price my white faced black Spanish or my Speckled Sussex since I don't expect either breed to sell as well as the Marans and Silkies and people can buy sexed chicks all day long at the feed store for under $4 each. And next year I will hopefully have bantam Ameraucana. But the projects and upgrades never seem to end. In chicken math.. we try not to talk REAL numbers!

But when I see others selling straight run chicks for $5 each... my thought most often is... meh, I can get that from the hatchery and not have to deal with someone else's possible parasites or disease for less $.

Good luck!
