Hopefully store prices will come down as the year goes on and flocks bounce back.
* Maybe 0.25 birds/square meter? There's ~12 total (we raise some for slaughter now, so it fluctuates) and they have a large enclosed outdoor area attached to the much smaller (6m^2, perhaps a bit more) indoor coop.
* Several acres. We let them free roam during the day with someone to supervise, but otherwise they have to stay secured (coyotes.)
* Inside the coop, the standard way is the "deep litter" method. You cover the floor in several inches of pine shavings and turn it over with a rake daily. Add a new bag of shavings here and there, and cycle it out completely maybe twice a year. The old bedding makes for good compost. If it doesn't smell, then you're good. For the outdoor area, we just auger it over and add mulch/soil around the same time the bedding is replaced.
(Note - tending to the birds hasn't been in my wheelhouse for a while, so don't take this as gospel!)