Starting out help!

Our house came with a chicken coup and we haven't done anything with it for the 6 years living here. Shame on us, I know! We're finally going to get it cleaned up and ready for our own. It's a homemade plywood coup and needs a little work before we can get chickens in it. What advice do you all have?

-how many chickens for this size? It's maybe about 6ftx6ft? I'd like some for laying and a few for butchering if I can

- it has a cutout on the one side for the chickens to go out of the coup and a space with 4x4s set up to put fencing around

-what supplies do you recommend? (plastic vs metal feeding/watering?)

-is there enough air flow? ideas how to fix?

-open to any suggestions that are as budget friendly as possible!

Thank you in advance!