Ooo, one of my favorite topics! I have had chickens for over 5 years and they are absolutely wonderful.
A chick is generally between $1-5, depending on the breed. You can order them from a hatchery, but you have to get them in batches of 25. You might want to look for someone or a few people to split an order with. Or better yet, find someone selling older pullets or laying hens. TSC also has chick days were you can buy chicks in batches of 6, but they are unsexed and only happen in spring.
Chickens do well on scratch feed and cracked corn, you can get that at any feed store. They love kitchen scraps, scratching for bugs, etc. Chicks need to be raised on chick starter (little crumbled feed). They need clean, unlimited water year round (though mine subsist on snow in winter most of the time, I do bring out a dish of water in the mornings but it freezes right up).
There are coop plans all over the internet. If you are only getting a few chickens even a dog house will work if you put in a roost and a door. We have an 8 by 8 wooden barn that you can get from Home Depot. They come in kits or prebuilt. We put up roosts and its perfect. Bed the chicken house with wood shavings or straw, though woodshavings seem to keep things cleaner and less smelly.
I am in Ohio. All chickens need in winter is a good draft free coop, deep bedding, and plenty of food. We have 2 doors on our coop, the regular door and a door inset behind it that has a little square cut out we keep closed in winter so the heat they generate says in. Do not heat the coop! We did this our first winter and it causes mold to grow which makes the chickens sick and kills off a good number.
Breeds- my favorites for Ohio are the Buff Orpingtons, Barred and White Rocks, Rhode Island Reds, Brahmas, Comets, Black Sex Links, and Wyandottes. They all lay well year round and some of the breeds go broody and will hatch and raise their own chicks (if you have a rooster to fertilize, of course!). Other breeds, such as ornamental/ fancy types don't do as well in the cold weather. We also have had many Americana/ Easter Egg chickens who do pretty well, but basically stop laying all winter. Bantams are colorful and fun, but have itty bitty eggs and occasionally foul tempers.
Hmm, what else. Take into consideration where you live. You need a pen for the chickens (chicken wire and t-posts are fine). If you have lots of land you can let them free range and they will return at night to roost. Don't do this until a few weeks after you introduce them to their new home or they don't know where to go. If you have close neighbors whose yards can be invaded by the chickens or dogs running loose keep them penned, because coming home to a yard of dead bodies and feathers is heartbreaking.
They are tons of fun and easy to care for.