Skills You'll Need: You must be attentive to details, and a good memory is essential because you may not be able to take notes while on assignment. (As a mystery shopper, your mission is to act like a regular consumer, so you don't to want to do anything that could bring attention to the fact you are evaluating the business.) You'll also need good record-keeping skills, so you can keep track out-of-pocket expenses, such as gas and car mileage.

Equipment You'll Need: A car is usually necessary for getting to and from the establishments you're evaluating, and a computer is needed for online shopping. A fax machine or email fax service is also desirable.

Start-Up Costs: Though you'll be reimbursed later, you'll have to lay out the money needed for each mystery shopping assignment. (For example, you'll have to pay the price of admission at the theater you're evaluating or cover the cost of groceries when doing a supermarket shop.) You bill the mystery shopping company for these expenses when you send in your evaluation form. Since mystery shoppers work as independent contractors, you will be able to write off any non-reimbursable expenses on your taxes.

How Much Can You Make? Anywhere from around $5 for a supermarket or fast-food evaluation to up to $100 for complicated, time-consuming tasks like opening a bank account or assessing the service at an airport ticket check-in counter. But most pay in the $20 to $40 range, and include additional incentives such as coupons for free dinners or movies. Some companies don't pay cash -- instead they'll only offer coupons, free products or services, or gift certificates.