Take a product or service. Simplify access to it and offer for less than other sellers.
If someone can just go on a website, select something, not pay as much as elsewhere and it arrives at their door, it’s an easy sale. All that is left is marketing.
But if someone has to call your or coordinate how to order the product and when it will arrive, never going to happen unless you own the market for that item.
I’m really only just getting started in my current business. I have a private practice where I provide a variety of services. I also work as a contractor for a few other companies. My income is basically what I would make if I worked one full time job but there is a lot of potential to grow whereas in a full time job that would be the ceiling.