Do you enjoy fast food or going into retail shops? Many companies hire mystery shoppers to test the customer service of their stores. A common one is Subway, which hires mystery shoppers to ensure that "Sandwich Artists" are following all the franchise guidelines. If you have time and can travel to different places, this could be a good side hustle.
Set up a merchant account. Service businesses in the past had to generally rely on cash or check—setting up an entire credit card processing system was a thankless, expensive task at best. Using a service such as PayPal makes it possible to accept virtually any form of credit or debit card for your services, and includes dispute resolution should the need arise (and it will arise).
Be professional. When you submit a résumé, don’t type it in ALL CAPS and please don’t avoid the caps lock like the plague. Know how to use it without looking incompetent. Write in complete sentences with proper grammar. Of course, there will be exceptions, but even with the exceptions, you must keep it professional. You’re building their view of you.
One of the easiest ways to make a few bucks online is affiliate marketing. An affiliate is essentially someone who receives a commission for selling products for other companies, whether it’s on their own site or through another channel like eBay. The best part is that you don’t have to develop any products yourself, just sell other people’s products.
Work at home transferring data from one source to another. Most of these companies do not require past experience, although with few exceptions the pay may not be enough to consider it a stable income. Before you begin applying to any of the companies below (many of which sadly are almost never hiring), you might want to read the post I wrote about data entry jobs from home. It explains what your expectations should be prior to pursuing a career in this industry.