Key aspects of a coop are:
-Access. How do you access the coop for eggs and maintenance? The run? How do the chickens get from coop to run?
-Ventilation. Ventilation, Ventilation, Ventilation. You want to have lots of ventilation to let out ammonia and to keep the air moving in the coop. As far...
Trust me, that number will eventually grow ;)
This is a summary of how owning chickens works:
I'm super interested to follow how you convert that playhouse! Have fun on your chicken keeping journey!
How many chickens you have also depends on how much space you have. You can have more bantams in a space than standards. Standard birds need 4+ square feet each in the coop, and 7+ square feet each in the run. More space is always better!
How many chickens do you want? ISAs are AMAZING egg layers of HUGE (I get MONSTER eggs from mine) brown eggs, but a downside is that they have a short lifespan usually caused by reproductive issues. I'd recommend getting a variety of breeds and not just one-having variation in egg color and...
That looks like a great plan! The elevation will be great for flooding. Just seconding what @Kireh said-make sure to have a good size ramp with the area around it clear. You probably want lighter, better flying breeds like bantams. Some good standard breeds could be leghorns. Anything really...