挨 has TWO pronunciations: āi (close to, in sequence) and ái (to endure, to suffer — see 挨打). 挨家挨户 (āi jiā āi hù) = house by house, door to door. 挨个儿 (āi gèr) = one by one.
grammar
As āi: 挨着 (next to), 挨个儿 (one by one). As ái: 挨打 (take a beating), 挨骂 (get scolded), 挨饿 (go hungry).
