Greetings and welcome to BYC Jeanette! So glad you joined us. LOVE what you're doing for the historical place and for your nephew! Please DO NOT waste you money on the prefab coops at
TSC or online. They are garbage! They will NOT properly house the number they state, and the quality of the materials is very sub standard. Good coops don't HAVE to be very expensive...
The $1500 quoted for the coop (size stated) is also too high unless he's building a chicken mahal. The size stated is too small for 12 chickens. As stated, buying one of those prefab sheds from Home Depot or Lowes and modifying it would be the simplest and probably most cost effective way to go, especially if your nephew has any craftsmanship capability and a few power tools. There is plenty of info and guidance available here in the coops section.
An adult large fowl chicken really needs ~4 square feet/bird INSIDE the coop and ~10 square feet/bird OUTSIDE the coop in the run. You can get a way with a slightly smaller run if the birds will primarily free range. But it IS a minimum if they will be contained within for any prolonged periods.
There's a wealth of info, knowledge and experience shared in the multitude of threads. Browse around and see what interesting stuff you can find. By all means post away when the desire strikes you, especially if you have questions (provide as much detail/info as possible and pictures truly help)... With all the great folks here, generally someone will respond in no time at all. Please make yourself at home!
Oh, if you haven't done so already, PLEASE put at least your general location in your profile. It could be very important if/when you ask for or offer help or advice. You know, climate issues and such. Old folks like me

will never remember & look there first. To add it, mouse hover over Account top right and a drop down will appear. Click on Personal Details and scan down. You'll see the spot for Location. Then go to the bottom and save changes. Thanks! Hope you enjoy the site!
Hope you pass on our site to your nephew. Would be great to have him join the fun here as well!
