Why the interviewer is asking this question: The interviewer is asking to align expectations for the role with your long-term expectations. While interviewers typically want solid alignment on near term (i.e. under 5 years) expectations, more latitude can and will be given for longer term goals.
If they don't want to give benefits to stocker and cashiers they should have part time hours and paid $17.50 per hour no benefits. Also how many teenagers would like a parttime job from 3 pm until 7pm and maybe get the pay they give their cashiers $8 -9 an hour.
Most of this advice is pretty accurate. What the mover told apt 23 - 5-10 dollars per hour per man - is definitely the most accurate. While you may be paying $120-180 an hour for the job, most movers in NYC are paid $12 an hour or less, some as low as $8, so tips are clearly meant to be part of the pay package.