Last month I made over $600 just working a few hours per week. I was able to work around my existing work and family schedule, and there were no long extra shifts or spending my entire Saturday working. In addition to that $600, I was reimbursed another $300 for my purchases—including one very fancy date night with my husband, clothes shopping, gas, and two restaurant meals. Since I was already planning on making most of those purchases anyway, that's almost $900 profit just from doing my normal activities!

How did I make this extra income? Mystery shopping! No, it's not a scam—it's a real business. Marketing agencies and retail companies want to know how best to serve the consumer, so they hire average people (like me) to give them detailed feedback on their company's products and customer service.

Mystery shopping is a flexible part-time job, allowing you to control how much or how little you work in a given week. If I’m busy with my regular job or family commitments, I will work less during that week. But the more I work, the more money I can make.

If you want to become a mystery shopper to make a fun and flexible side income, here are some tips that have helped me.

Learn the ropes

Mystery shopping is a job, and though it’s fun, it requires real work. When beginning mystery shopping, remember to take it seriously and pay close attention to the job requirements. Download a stopwatch app on your phone, text yourself notes during the shop when needed, and keep your eyes and ears open.

Mystery shopping requires specific interactions with customer service representatives, which includes—specific questions to ask and specific purchase requirements. You have to follow all of the requirements or you risk not getting paid. Start with one mystery shopping company and one type of shop that you can become comfortable with as you learn the ropes. Once you get that down, try another shop type and branch out from there.

Sign up for multiple mystery shopping companies

Experienced mystery shoppers shop for multiple mystery shopping companies. Personally, I’m signed up with 31 companies, and I shop about 15 times every month. Each mystery shopping company has its own client list and a limited number of shops available in your area.

In order to keep busy and find a variety of shops you can schedule for yourself, I recommend signing up with a few companies that have a lot of shops in your area. Large metropolitan areas will have more shops available than smaller towns—so if you live in a big city you may only need a few mystery shopping companies to keep you busy with enough assignments.

Keep track of your shops and stay organized

Keep a calendar and write down every shop that you’ve scheduled for yourself, as well as other activities you’ve planned. This will keep you from over-scheduling yourself and from forgetting what you need to do and when.

Keep a spreadsheet of all the shops that you’ve completed and when, as well as how much you’ll be reimbursed and how much you’ll be paid. Mystery shopping companies usually take anywhere between two weeks and two months to pay you. Make sure you know when you expect to get paid and that you can keep track of it.

Also make sure to track your mileage and pay taxes because mileage is deductible and all earnings are taxable (though reimbursements for purchases are not). Keep all your receipts and shop notes at least until after you get paid (or for longer if the mystery shop company requires it). After that, just keep your receipts for tax purposes.

Below are a number of reputable mystery shopping companies that I recommend: