Well, yes, but that's why you quarantine for two weeks first. Then you can watch for diseases or parasites. But whatever works best for you!We did that once and he introduced chicken lice into my flock which was previously disease/pest-free. So, while I'm very happy with him now that he's integrated and we treated our entire flock and coop area, and he's protected our girls quite well, I will opt to avoid bringing in any poultry that is NOT day-old. It could have been worse than just a case of lice. It could have been Mareks or some other awful disease.

https://www.backyardchickens.com/articles/adopt-chickens-in-need.79320/