Welcome! Check out the Articles section of the Forum, and especially the Coop Building Articles, and the articles on predator protection. There is a lot of information.
Since you're in SE GA, I'd recommend building an open air coop - basically a three sided lean-to with a roof connected to a secure run, or a Hoop Coop - one of them might be perfect for you since you only want three chickens. You'll need lots of ventilation above the chicken's heads - 3 square feet of ventilation per chicken. Pretty much all of the pre-fabricated coops you'll find in the store are inadequate wastes of money and don't have enough space or ventilation for full size standard chickens - do lots of research before you commit your dollars. Do you want standard large fowl chickens or bantams, which are significantly smaller in size (but also lay smaller eggs)?
Minimum floor space recommendations for standard large fowl chickens are 4 square feet per chicken in the coop plus 10 square feet per chicken in the run. 3 square feet ventilation per chicken in the coop, above their heads. Should try to keep the coop draft free and dry. 1/2" hardware cloth is needed to prevent predators from eating your chickens - chicken wire only keeps chickens in, does not protect at all from predators.
Anything you can get for free will reduce your build costs, and converting an already present structure is often the cheapest option. I found that purchasing a coop and making needed modifications (a lot of them were needed!) or building from scratch (more space for dollar spent - best value), either had a steep price tag. Cost things out before you start. $1-2K for a stationary coop and run is not unheard of if you have to purchase and build everything new. Could get it down to under $1K if you are able to repurpose or obtain a number of things for free. But once you have everything set up, you could get years of use out of it.
Hello and welcome! I’m in Georgia as well and it’s very hot and humid. Ive had Orpingtons, australorps, Wyandottes, and Easter eggers for 3 years now and they seem to do fine in the heat! Just need lots of shade and always fresh cool water