So you are thinking about quitting your job and going solo? Before you do, you need a plan for where your income is going to come from. This should be split down into Active and Passive income.
For example, for Active income, this will be things like contracting, consulting, where you are exchanging your time for money. This is great, but once that time has been spent, you will not earn extra for it.
With Passive income, you will spend time producing work, such as an ebook or online course, and once it has been put live, you will earn income off of it from there onwards with no extra work.