There are opportunities to earn small amounts of money—and get free products with mystery shopping services—depending on where you live. Some people may manage to make a living at this, but it is not recommend that you rely on it to pay the bills, as assignments can be very sporadic.
Don't get ever pay to become an "official" mystery shopper, assuming you'll automatically get hired. A legitimate opportunity should not cost you any money. It should give you the chance based on your profile, interests, and background.
One resource in learning more about the industry and finding links to opportunities is The Mystery Shopping Providers Association
Finally, always remember to review the details of any opportunity before signing up so you're clear on what's expected and what type of compensation you'll receive.
