Keeping chickens is great! Chickens can make great pets, particularly if raised by you from a chick (as you can get them used to being held etc.) Chickens can live for around 10-15 years but 5-6 is pretty good going for most breeds. Commercially, laying hens are usually kept for about 2 years and then replaced. In fact they can lay for much longer than that (quite often 5 or 6 years and more). As they get older egg production does usually tend to slow down (and eventually stop), but it is not unheard of for an elderly chicken to give the occasional egg or two a week for the whole of its life.
Fully grown chickens need a comfortable place to live. Chicken coops range from basic adaptations of an existing dog kennel or shed to full-blown bespoke poultry palaces. It does not really matter to the chickens (luckily they aren’t able to see what other chickens have!). As long as it is comfortable, dry, free from drafts (but still with ventilation) and secured from predators (such as the fox, skunk, mink etc.) they will be happy. It is usual to allow 1 nesting box for every 3-5 chickens (although you may find that the chickens have different ideas, and decide to cram themselves into the same one!). They also like to ‘roost’ at night so a roosting pole is a standard feature. In the day time they will need to be able to scratch about a bit – a secure run is fine for that (you can let them loose in your garden if you have secured it from predators – and don’t mind them eating all your flowers / veg!).