I have been reading here for a long time and was happy to just read but I can share regarding your question on quail
I've a particular fondness for quail. They're nice little birds, the eggs are excellent despite the small size, and I think the meat sells well enough. This is one of those animals that you can't really free-range, but I'm not too fond of confinement for animals, especially the really tiny cages they're usually raised in. Hoping for a free-range method might be asking too much, but is there a way to raise them with more leg & wing room? The local Ag. Department was getting good results trialing big growing cages on whole plots of vegetables like peppers (it keeps the pests out, and leads to a much bigger harvest). Could quail be integrated to such a system, or would they eat the crops?
I have a mini permaculture style farm where we just grow food for us and a few friends. It's not serious, just for fun. I run a few of these tractors for quail. Currently working on mk11 versions though to fix some issues with these. The birds do great in tractors on a small scale, this doesn't necessarily translate to the scale you would need for profit though.
If you want details -
http://boobookfarm.com/quail-tractor-build/