You've thought about it. How can you make money on the side? You have a job that provides income, but you can't help thinking that with your spare time, maybe you could make some more money.
While not ideal for everyone, if you have special knowledge, and an avenue to reach the public, you can probably start a consulting business. There are literally millions of people that want help or knowledge, and don't know where to turn. Or they don't have time to learn something. But they have an internet connection and like to use Google. So if you can reach them, they are a potential client for your new consulting business.
That is where you step in to fill a need. You either have unique knowledge, or you have been through an experience that gives you special insight into a process. For example, I left my life insurance employer to start my own RIA (registered investment advisory) firm, and it posed some special challenges that made the decisions surrounding it more difficult. Financial advisers that started in the insurance industry have considerations that non-insurance financial advisers don't have, and when they plan to leave to form their own RIA, they need special assistance or coaching. That is my consulting business.
I act as coach/consultant for financial advisers looking to leave their insurance company because they are tired of quotas or because they want to engage in a fee-only investment advice. This has proven to be a really nice consulting business, and I feel like I am providing a service they really need. And since I charge $90 per hour, if I spending 5 hours during the week coaching, it can add $450 in extra income to my weekly income.
So look at your own special skills or insights. Or increase them if you don't quite feel confident enough to provide the advice. There are likely tons of people searching the internet right now to learn how to do something, and you could fill that need.
I am a Chicago-area financial adviser to young doctors & business owners.