New guy with question
It is true that they can have liquid come up from their crops when they are held upside down. But as previously said, watch them closely for any noisy breathing (wheezes or rattles,) gasping, nasal drainage, watery or foamy eyes, sneezing, or swelling around an eye or the face. If you see that, I would recommend taking them back or putting them down, since you don't want to start a flock with a chronic respiratory disease that will infect any new chickens you bring in. Buying chickens from anyone is a crapshoot--you may get ones that look healthy, but are carriers of a disease or become sick due to the stress of changing homes. I usually tell people who start flocks to buy baby chicks from a well known hatchery where you have the best chances of not introducing a disease.