$15.00 a hen is about the going rate for a young hen before her first molt.
After a molt (about 1 1/2 to 2 yrs old), $10.00 is what they are selling for around here.
It all depends on whether you want to raise your own and wait for 6 months to get eggs, or have the eggs right away from grown hens.
If you buy hens, make sure you buy from a reputable breeder. Some will sell old, used up hens after a molt as young hens.
Also look at their beaks, if they bought old battery hens to re-sell, their beaks will all be trimmed. (Now, started pullets from a hatchery will also have their breaks trimmed, and they ship them out at about 16 weeks of age.)
Either way, the cost per chicken will be comparable to each other, you can fork it out all at once or spend a little at a time over the 6 months it takes to get chicks grown to laying size.
We have plenty of shade, I change their water at least twice a day when it gets really hot, sometimes I put ice in their water. We have fans in the hen house, and I will water down their run. They enjoy the water in their run, they have scratched out several holes and I fill them up with water, they love to scratch in the wet dirt and run through the water puddles.
I think any color chickens will do good with proper care. We have had Black Australorps, Black Sex links, and Black Sumatra's. The heat didn't seem to affect them any different than the lighter colored chickens. I wouldn't raise chickens here if I had to keep them locked up in a coop 24/7. The heat would be too much for them if they had to stay locked up.
Jean