Hello,
Maybe things have improved in this sector, but years ago, it was a terrible (part time) job.
You'd get communications at short notice, to go to certain specified stores and make purchases (of very specific items), and with tight deadlines to complete the task.
Receipts were collected and submitted to get refund on items purchased, with payment of out of pocket expenses often slow to be refunded to you.
Any errors (ie the wrong size bar of chocolate etc.) or missed deadlines for completing the task and uploading required evidence of item purchased, and you were out of pocket.
Between the value of my personal time, the commute costs to specified shops, and the unreasonable notice periods, plus tight deadlines that were imposed, I'd be very slow to encourage anyone to get into this, tbh.