Even though the best time to start a business is while you are at a job, it has its own risks. You have a backup income that doesn’t put a minion of pressure on your startup timeliness and you will anyways be busy with your day job. However, the slow pace of your startup will eat up your finance and your productive months. This overlap would easily go on for 3yr plus until some real heavy external trigger like a job loss or near ones passing away pushes you against the wall. At that point you should have cash flow coming into your business and if not you are already on a sinking ship.
So how to make sure your business is cash generating from the moment your other options are cut in a flash. Its back to basics which is to complete all your homework. That means close your decisions and actual paper works on: