The consequences of running out of money are real.
The question OP raised isn't preparing for money running out, it's presupposing failure.
How much do you start with, what's your burn rate, how long until you get revenue, are you bootstrapping/funding, your personal cost of living, etc.
Running a business involves risk. Risk to your comfort, your mental health, physical health, financial health, etc. Closing a business is the end of all of that, not the start.
Why do you want to scratch that entrepreneurial itch?