One problem I’ve run into is that whole chickens from the supermarket have usually been frozen. Sometimes when you buy it the outside seems thawed, but the inside is still frozen fairly solid. If you cook the chicken without knowing this, you’ll end up with perfectly cooked to overcooked chicken on the outside with a cool salmonella center.
As such, I always buy chicken the day before I want to cook it (leaving it in the fridge), or I buy one that I can be pretty sure hasn’t been frozen.