I got into chickens about 3 years ago and I now have 35 of various breeds in several coops. 3 of the coops I use are prefabs bought from
TSC and
Amazon. They are flimsy and I've had to paint them and put new roofs on, but they work well for 3 or 4 chickens. Note that they were advertised for 6 to 8 chickens so buy much bigger than you think you need. They have lasted well for 2 years and will probably be fine for another few years. I built a level foundation for each of these coops from 2x4s and that lifts the coops up and keeps them from rotting as quickly. I got these because it takes time to build a coop yourself and my flock was expanding more quickly than I could build.
I can pretty much guarantee that you will find things "wrong" with your first coop, no matter how much research you do. There are some things that just won't become knowable until you get some experience and find out how you like to do things and how things work in your climate. I'm in the process of designing my 3rd coop now and I'm sure I will find ways to improve it once I start using it. Some of the things that I've found out that the chickens love: a covered but open spot with a roosting bar that's safe so they can sleep "outside" when the weather is warm. A dry place for feed and water that's right by where they spend time in the daytime. Almost all of my coops have an enclosed run under the coop that is secure so I leave the coop door open and they can stay in the coop or be in the enclosed run at all times and still be safe from predators.
Shade and ventilation are going to be extremely important in Florida - don't worry about the cold (I've had chickens shrug off the snow that fell on them with no complaints) but the heat there can kill chickens. Make sure they have a shady spot where they can cuddle down into some moist soil or sand. You may also need to add some sort of misting system or at least wet the area down in the morning. Don't feed them any corn in hot weather since it tends to raise body temps. Give them some treats of fruit or veggies frozen in ice. This way they have a continuing source of small amounts of something cold to eat & drink over time. They may also need supplemental electrolytes in hot weather. I would recommend breeds that have large combs, the combs act as heat radiators to help them cool down.
Predator protection is also a key. Everything loves a chicken dinner. So you have to have a plan that will protect your chickens from every possible predator both large and small, on the ground and in the air. Half inch mesh hardware cloth is your friend. About the only thing that can get through it is a large dog (or a larger predator like a bear. I think we can discount bears where you live.), and the mesh is small enough to keep out rats, lizards and snakes. Any hole in the fabric of the coop that's larger than half an inch should be covered with some hardware cloth. For dogs a 6 foot tall fence will work most of the time but there should also be something to prevent digging under the fence. If you can't bury wire deeply for some reason, laying wire fencing on the ground for 3 feet on the outside or inside of the fence will probably work too. One thing to beware of is that raccoons will reach through a fence if they can and grab whatever part of a chicken they can grab, pull it up to them and start taking bites. If you can't make the holes in the fence too small then keep the chickens away from this fence. You can use layers of protection, so one fence doesn't have to keep everything away. For aerial predators like hawks you can cover an area with wire fencing or hardware cloth or a solid roof. I use a flexible hawk netting I bought on
Amazon, it comes as large as 50 feet by 50 feet and it works very well. It has stood up to sun, snow and ice for 3 years now with no sign of disintegrating. And I've seen a hawk bounce off of it so I know it works. Using this I can let my chickens out to run in the garden without worrying about hawk attacks.