Yes Chickens are cold hardy or heat hardy dependent on the breed. It is really important to get a breed that suits your expectations and climate. Not all bird are high egg layers, but keep in mind that a lot of high laying breeds can develop health issues and can burn out. The famous sex changed hen from the UK developed rooster traits when her ovaries stopped functioning properly, she was an ex-battery rescue. There are also some breeds that have been selectively bred to lay so many eggs that they MUST eat the correct pellet, ISA is what we have in Australia that falls into this group. ISA must eat the correct pellet and hardly anything else because the poor birds crank out so many eggs that their bodies can't keep up otherwise. If you want birds for more companionship and are not worried about eggs silkies or penkin are options, they lay more irregularly... and 1/2 size the eggs you are used to. For me eggs are just little gifts I get sometimes, and I only eat eggs from my birds. I don't care if I do get eggs and my flock has 1 bird with scoliosis, 1 elderly hen, and 1 pekin.. I haven't had an egg in many months, which is fine by me!
I found this like from MSU might help you decided on a good cold hardy breed for Illinois.
https://www.canr.msu.edu/uploads/234/69325/Chicken_Breed_Chart_to_Help_Choose_Your_Chicken.pdf -some of the breed generalisations are hilarious! Each bird is definitely a little unique and not exactly how this document states.. my ancona rides around on my shoulder and is the sweetest hen.
Also check the regulation in your area for rooster and hens the numbers that you can keep for example:
Tired of your neighbor’s rooster? Chicago could soon crack down on backyard farm animals.
For medical care chickens require a regular deworming schedule since they can free range it is easy for them to pick stuff up. It is also important to provide them with calcium grit. Even if you have a pelleted feed with some shell grit, the hens can decide to eat more and they need to eat more for their health time to time. I am most amazed by my chicken's talent for self regulating. For feed, I do a layers pellet and vegetables and fruits. They also get to free range for a few hours a day. Their normal coop is 18 sqm for my 3 birds and I set up swings, logs and a sand bath. I would let them free range all day, but I do not have a fence yard and our neighbors have dogs...shucks! I have a dog! So I needed to provide a large coop. My coop is full height and I can walk in the door and stand comfortable, which helps immensely with cleaning and companionship. Within the coop is the hen house which I built, and should probably design and build a new one. I have had it for 5 years and some ants have started living in the timber :O
Chickens are wonderful birds as are quail. I personally have much more experience with chickens. My close friend kept a flock of button quail and most of my quail knowledge come from sharing her experience.