Welcome!
If the structure is sound then it's great to have a building to work with, especially in this day of high lumber prices. That's the first thing -- get someone who really KNOWS building to give it a good look-over to make sure it's sound and safe.
Where are you located, in general? You can put it in your profile so that we can give the best-targeted advice for your climate and likely predator load.
Here is some general information:
First, space requirements,
The Usual Guidelines
For each adult, standard-sized hen you need:
- 4 square feet in the coop,
- 10 square feet in the run,
- 1 linear foot of roost,
- 1/4 of a nest box,
- And 1 square foot of permanent, 24/7/365 ventilation, preferably located over the birds' heads when they're sitting on the roost.
Two things to remember about this. First, these numbers generally represent *minimums*. Second, they are
guidelines, not hard-and-fast
rules. Here's a good article on this:
https://www.backyardchickens.com/articles/how-much-room-do-chickens-need.66180/
And a useful thread:
https://www.backyardchickens.com/th...ave-more-than-the-minimums-for-space.1462570/
Second, what do you want chickens for? Eggs? Meat? Eggs-and-Meat? Bug control (to answer one of your questions, chickens eat ticks and help reduce the tick population on a property)? Gardening? Beauty? Showing?
Here are some of my thoughts on choosing breeds:
https://www.backyardchickens.com/articles/go-ahead-pick-the-prettiest-chickens.76277/
Third, Predator Protection. Knowing your general location will help us give better advice. For example, in my part of NC we DO have raccoons, coyotes, stray dogs, weasels, foxes, hawks, owls, and other predators, but we DO NOT have bears, mountain lions, or badgers.
The predators we have can usually be deterred by 1/2" hardware cloth. Bears can only be deterred by STRONG electric wire.
And some of your questions:
Should I put anything down on the floor? Or on the ground outside?
While some people do use nothing but bare dirt, most people like to have some kind of bedding in the coop and litter in the run. This is my article on my favorite method, but read about other methods too because there is no one right way to do chickens.
https://www.backyardchickens.com/articles/using-deep-bedding-in-a-small-coop.76343/
Would they like a trough of water or just a watering bucket with nipples?
There's an interesting thread on that subject active right now:
https://www.backyardchickens.com/th...e-waterers-in-your-opinion-yes-or-no.1476555/
What should I put in their laying area? Straw?
Another area of debate with no one right answer. I like shavings with some straw or dried grass clippings mixed in. Some use only shavings. Some use straw. Some use hay. Some use commercially-made nest pads.