We had six chickens when I was little, was great to have fresh eggs. But they got killed by foxes eventually.
Then my Mom decided to get some again when I was a teenager. From what I remember it cost quite a bit for a good quality secure hen house. And the enclosure needs to have the chicken wire walls dug down and buried into the ground otherwise the foxes can pull it up if not secure enough. Despite all this the foxes got all of them one night when they were not shut away in the main hen house at night.
Don't let that put you off! I think it would be a great thing to do, depsite the initial cost of the hens and the equiptment and food etc, in the long run it will save you on buying eggs, and you can always sell the eggs too! And the sound of hens is so friendly and warm as they cluck at you in the morning. And you cal tell when they are laying an egg....squaaaaaaaaaaaaawwwwkkkkk!!!!