A lot of it depends on your breed. If you want good tail feathers on the males, they need room. If you are just raising them for meat, they are very similar to chickens in space needed. Also, some breeds will need to be bitted, or even blinded to avoid fighting. Something else, pheasants like a lot of cover to make them happy. Good luck!
As was mentioned in the above posts, it does depend on the species. One of the best species to start with would be the Golden Pheasant - beautiful colors, readily available, modest in demands and small in size. They can be kept in fairly small sized aviary, just ensure plenty of cover and enrichment. Phasianus (true pheasants - i.e. ringneck) are rather flighty and nervous birds, but often seen as a "first" species, would need a larger aviary as would other good beginner species such as Lady Amherst, Silver and Reeves.
My FIL wants to get some ringneck phesants. His existing chicken coop (no chickens) is 10x12. He plans to raise them and let them go into the wild when they are fully feathered--or how long should he keep them before releasing them?
Does anyone have advice or experience with this???
Are there other considerations for housing, etc.??