Chickens are probably the easiest and cheapest farm animals you can keep. They only need some space, some cleaning, water and food (it sounds harder than it actually is). My family has had chickens for a while, my grandparents did too and I thought I should write this simple guide for everyone that hasn't had much experience but is nonetheless interested in having a chicken farm. I'll probably keep updating this guide with more information in the future. It's also important to note that some of it may also be dependent on other factors, such as the sub-species, the age, the climate etc.
Everything that comes out of a chicken is useful in some way. This is not an exaggeration: even the rooster's crowing, which some people consider annoying, is an excellent reminder of your circadian rythm (this is a whole different issue on why you should keep your sleep in sync with the day cycle).
Chickens can live up to 7-10 years, however egg production lasts only for the first 3 (max 4) years of their lives. Hens start laying eggs after 3 to 5 months of age. Generally, they produce fewer but larger eggs as they get older. My experience is that one or two year old hens lay one egg per day each, and as they get older they produce less.
It's important to note that the egg quality is much better than most eggs found in the market. Especially for older hens, they taste a lot better and can be twice even three times as large as common eggs.
You can slaughter a hen after she stops laying eggs. Their flesh is generally hard to chew on compared to most chickens on the market, but your jaw probably needs some exercise, anyways.
Keep your chickens in a comofortable space with grass and dirt. They also need to have a closed coop or henhouse, or at least a relatively closed corner where they can feel safe and sleep. This can affect the egg production. Make sure their space has a good fence! It should be obvious why: not only are there many predators lurking outside, but chickens are smarter than you think. They can dig beneath the fence, fly above it etc. and they can generally find quite impressive ways to escape. The fence should extend beneath the ground.
You'll want to clean their space from manure, especially during the summer and during the deep winter, when they stay all together in the same place for warmth. How often is entirely dependent on the number of hens, however a quick clean once a week seems to be fine. The more often you clean it, however, the better. Unlike many others promoted nowadays, this is a situation in which you want to wear a mask and a pair of gloves. Their manure is a great fertilizer.Feed them whenever their food runs out. Their diet mostly consists of wheat, cereal grains, soya etc. although they also eat insects, especially flies, crickets, grasshoppers and worms after the rain. Make sure they have clean water.
Even if you don't want fertilized eggs, you should definitely get a rooster. Not only do they protect the hens from possible predators, but their mere existence helps with their psychology and, thus, their egg production. You'll want about one rooster per ten hens if you just want eggs. If you want to breed chickens you'll want more roosters, as much as one per two hens. However, having many roosters can be a problem for small flocks as they are competitive. They generally get along in larger flocks, though.
Roosters can crown whenever, although they mostly do when the sun rises. From what I know, it's impossible to make them not crow, so if noise is an issue you'll want to think about that (especially with more roosters). Roosters can be aggressive. In the unlikely scenario in which you have to grab one of them, get close, charge at it and grab its leg. It's the only way to do it without getting bitten.
Hens lay their eggs early in the morning, you'll have to collect them as often as you can, the most often being every morning. They generally prefer to lay their eggs in kind of hidden and warm areas and they seem to particularly like hay. One thing we did to help the process of collecting eggs is, we made a basket with hay, tied it with a rope on a balcony above the hens and place it on the ground. Although it didn't always work, most of the times the hens layed their eggs in it, and we just pulled it with the rope every morning. In case you cannot get yourself to eat all the eggs you produce (which is very possible), don't be afraid to share them with your neighbors. People remember and favours are returned.
Mice and gophers, and maybe even dogs can eat the eggs. Dogs specifically may scare the chickens too, so try to keep them separate (although it seems that after a while they start to get along). You might wanna get cats for the mice. Even hens may start consuming their own eggs, which is something we had to deal with in our farm. In that case, you should collect the eggs early in the morning. Alternatively, you can slaughter the hen that is consuming them.
For breeding, you'll probably need more roosters to get better results. Incubators are really helpful, as they protect the eggs and provide a constant ideal setting. Chicks should start popping out after three or so weeks, and they're quite vulnerable. After hatching, you don't have to feed them for around two days, however you need to make sure they're in a safe environment with heat. This may be an urban legend, but if they are older, and there are hundreds of them, if you have to place them in a box, make sure it's a round one(otherwise they will stack up on corners and suffocate). Make sure they have food and water at all times. Be very gentle with them and avoid holding them for the first few days. They generally eat fruits and vegetables, but you can also feed them small bugs. They have to be at least one month old before they go outside, and they will start laying eggs three months after that.
I hate to say that it depends. The more chickens & the longer you keep them for, the more it's worth it. They do, however, provide a reliable source of rich-in-noutrients food and that only makes them really worth it for many people who value autarky, including myself. One thing is for certain, though: you'll never like market eggs the same way again.