Для первого предложения:
1) What is your job?
2) Where do you work?
3) What type of shop do you work at?
4) How long have you been working as a seller?
5) Do you enjoy your job as a seller?

Для второго предложения:
1) What type of goods does she usually buy?
2) Why does she never buy substitute goods?
3) Have you ever seen her buy substitute goods?
4) How does she feel about substitute goods?
5) Are substitute goods more expensive than normal goods?

Для третьего предложения:
1) What type of goods does he buy?
2) Why does he always buy normal goods?
3) Are normal goods better quality than others?
4) Have you ever tried the normal goods he buys?
5) Does he have a preference for certain brands of normal goods?