I've kept backyard chickens for more than 10 years, 2 or 3 at a time, so I'll jump in.
In the spring you can find chicks for sale in feed stores and sometimes in odd pet shops. Bantams are often showy but are straight run--you won't know if you got pullets (young hens) or cockerels (young roosters) until the cocks start crowing. Bantam hens do lay perfectly edible eggs, but they are small. If you go that route get half a dozen chicks, raise them (in a big box in the garage with a heat lamp to keep them warm until they are fully feathered), and butcher the cockerels when they start crowing. (BTW, skin them rather than dunking the dead birds in boiling water and plucking the horrible wet feathers off.) With three hens, when they are adults, you will get about 2 eggs a day for 7-8 months, no eggs in the winter. If you go for full-sized chickens you can generally get sexed birds--all layers or all meat birds. White leghorns are egg machines, and nervous. If you plan to eat your old layers, don't get these, they are just bones. Black Stars and Red Stars are meat birds, but the pullets are sold as eggers. In my experience they have fragile egg shells, and only medium sized eggs. Easter-eggers/Americanas are novelties with medium sized blue and green eggs. Pretty much any thing else the feed store sells will be a dual-purpose bird. These are calmer birds, generally have large to extra large eggs, and have enough meat on them that you could stew the old hens if you really want to eat a pet. Most feed store chickens will lay brown eggs (white Leghorns lay white eggs).
Chickens don't need expensive quarters. I've seen yuppy chicken coops that were twice as much as I'm spending on my trailer frame. Mine live in an insulated dog igloo with split clear plastic panels hanging down to keep the wind from rushing in. The top lifts right off when we are searching for eggs or changing their nesting material. They have a deep layer of shredded bills and credit card offers that they nest down in. They do NOT have a roost, they stand on the crest of the roof when they want to be up high. The dog house/chicken coop is inside a "portable" dog run, 8 ft wide by 10 ft deep by 6 ft high chain link fencing. Chicks can go straight through the chain link fence, but when they are than small they should be in a big brooder box in your garage or laundry room. I also have a length of garden bird netting (this is fabric netting, not chicken wire) across the top, as I had a real escape artist for a while. Every spring and fall the dog/chicken run gets wrestled off the ground by 4 adults and moved over either 8 ft (a different section of my veggie garden) or the whole width of the yard (to the part of the yard that is sunny in the winter). I then put concrete pavers side by side all around the perimeter of the run, to keep critters from digging under the chain link fencing. My whole yard is fenced also with a 4 ft high chain link fence, which is high enough to keep a fat old hen in the yard, but not a spry young pullet. It also isn't high enough to keep coyotes, raccoons, or skunks out. The coyotes (and BAD dogs) will make off with a free-ranging chicken before you can blink. Raccoons will reach right through the chain link fence and grab sleeping chickens that are outside of the dog house/coop at night. They can also climb over the 6 ft chain link fence, giving another reason to cover the top with bird net. Young skunks can squeeze THROUGH the chain link, but fortunately they only eat the eggs. Rats and adult snakes can also be egg eaters. Chickens, OTOH, can be baby rodent and baby snake eaters. Funniest thing in the world to watch hens with baby garter snakes in their beaks chasing each other around the yard.
Okay, when I'm in the yard I do let the chickens out of their run. But they are messy, pooping on the patio and near the back door, scratching up plants in the veggie garden, making dust wallows where the tomato seedlings just got planted, that sort of thing. I have some sections of 36 inch "garden fence" that I put around the veggie garden and the pea/sunflower spiral, but sometimes I discover my fat hens can still fly that high, and they are safely IN the garden scratching away. Oh, and they LOVE to help find grubs and earth worms in the spring when I am turning over the garden. Yup, they come running when I get out the spading fork! However, THEY MUST BE FENCED AND IN THEIR COOP AT NIGHT! Even in Littleton you will discover things come out at night that will maim, kill, and eat your pets (and yes, they will become pets). When they are new to the run and coop, they won't know to go inside the coop at sunset. They will fall asleep next to the fence and the raccoons will find them. You will have to be Mom and put them in the coop every night at sunset until they get the routine. It will only take a week or two. Do NOT put any sort of roost (say a tree branch) through the fence. Dumb chickens will roost next to the fence and the raccoons will find them. If you want to give them a roost, put an old saw horse in the CENTER of the run, AWAY FROM THE FENCE. But don't let the chickens get in the habit of roosting there at night, or you'll have to re-teach them to go into the coop an night during the winter. (Does it sound like I've done all these things? Yup, I have some sad stories.)
I've lost chickens to coyotes and to raccoons. The coyotes run off with them. It's sad, but it's over quickly. Raccoons kill and eat them right there, and leave the surviving hens (and any kids in the household) with PTSD (and the hens not laying eggs). I hate raccoons!
My chickens have a heated dog bowl for water (not plugged in during warmer seasons), and since we check on them every day we don't have auto-fill. They also have a large rabbit feeder hung on the fence and dispensing their pellets and scratch. They don't need as much calcium when they aren't laying, and they need more carbs for warmth, so they get layer pellets and scratch half and half in the winter. When they are laying they get straight layer pellets (the pellets have the calcium in them already so I don't have to also offer shell). The food is in the dog/chicken run, but outside of the dog house/chicken coop. The rabbit feeder has a sloped lid and overhang, and a mesh bottom, so even in moderately damp weather the feed mostly stays dry enough for the chickens to finish it off before it petrifies or gets moldy. In a wetter climate I would put some sort of shelter over it. I prefer to hang the food at beak height than to put a feeder on the ground. They will poop in anything, including food and water bowls. I am okay dumping the water bowl once a day (especially as I can dump it in my veggie garden), but I'm too frugal to dump the food dish every day. When it snows, the chickens stay in the coop (which has its clear plastic hanging door flaps facing south) until there is some sign of melt. Where we live that is generally within hours of the snow falling. If the weather stays bad, we put them in a pet taxi and keep them in the laundry room (we don't have a garage) until all better. The dog house/coop is not heated, and two chickens can only generate so much body heat, so when the temperature is forecast to be below 20 F at night, we bring them in.
During the growing season they also get all the weeds pulled in the garden, the trimmings from veggies, and any bugs and larva picked out of the veggie garden. Chickens LOVE tomato horn worms, corn ear worms, and cabbage worms!!! They also love overgrown zucchinis, all red tomatoes, and post-Halloween pumpkins.
Chickens are social animals, so if you only have one it will chase your cat (or dog) around the yard trying to be a friend. Herding dogs are okay with chickens, by the way, but retrievers sometimes get too rough when the chickens stray and need to be "retrieved." Cats find them annoying, and will give you THAT LOOK, to let you know you are as crazy as your chickens. No large pets should be allowed near the young chicks.
Watch the movie "Chicken Run." Before you have chickens it is just a funny movie. After you live with chickens for a while you will start to recognize some of those birds!
BTW, if you get turkey chicks (called poults), name them Thanksgiving and Christmas. Sadly, I would say name your first chickens Raccoon Bait and Coyote Bait. But don't name your hens Lunch and Dinner, or other meal names. That's just mean, and unless your are a hunter or from a farm family, you aren't really going to have it in you to eat them when they slow down their egg production. And they don't slow down as much as the commercial operations would have you believe. I only had one chicken make it to 5 years, and she no longer layer 6 eggs a week, she was down to 4. But they were BIGGER eggs than the younger girls produced. Anyway, the whole point of backyard chickens is the eggs, not the meat.
Catherine