Yes, that's right - the initial outlay is expensive, so you need to do your research and get it right for your own circumstances. Many people go into chicken keeping by buying a cheap wooden coop which is too small, leaks, and has a tiny attached run which is totally inadequate for the space the chickens need, on the basis of what the manufacturers say about how many hens it will hold. Then, the next year, they have to start over with what they should have got in the first place. If you can afford a new plastic coop, you'll never have to treat it with preservative or use all the anti-redmuite powders etc that are involved with a wooden coop, and if you move house, or decide chickens are not for you, you can easily disassemble it and sell it if need be. And at least the hens themselves are not very expensive to buy or to look after, and will partly pay for their keep in beautiful eggs that you can trust for your family.
How many are you planning to get? Everyone who starts up from scratch has the urge to fill the run, of course. With 100 sq feet of room, about 9 sq. metres, you will have room for 4-5 medium sized hybrids. But bear in mind that they will each lay nearly every day for the first year, ie 2-3 dozen eggs per week, and unless you have very hungry family, friends and neighbours that's a lot of eggs! Also, if you stock to capacity at the start, after three years or so egg production will decline as they will have used up most of their egg cells and you'll then have a run full of pensioners for the next few years, that you won't want to cull because theyr'e pets. So, if you got 3 this year, you'd have plenty of eggs and could concentrate on training them to be tame and companionable, and then in Autumn of the second year you could give in to More Hens Disease get a couple more (you should always introduce a minimum of two at a time as a singleton will be bullied, and do it in the autumn as hens are less territorial then.) Subsequently, as they drop off the perch the other end of their lives, you can get another two whenever you have room, egg production will stay steady and manageable from the younger birds, and the oldies can enjoy their retirement.