Most people think you need a complicated budget or the latest app to stay out of debt. Warren Buffett does the exact opposite.

The billionaire investor has stuck to the same basic rule for decades, and it's one that almost anyone can follow, even if you're not great with money. He simply avoids spending money he doesn't already have.

Seriously, that's it.

Buffett's habit: Only spend physical cash

Buffett has long preferred using actual cash for everyday purchases. Not credit. Not even debit. Just cash.

Why? Because it forces you to feel every dollar that leaves your hand. When you pay with plastic or tap your phone, it's easy to disconnect from the money. But when you carry around a set amount of cash, you naturally become more mindful.

That one habit has helped him avoid personal debt his entire life. He's even said, "If I owe anybody anything, I want to get it paid."

Why most people don't do this -- and why it still works

Let's be real. Most people don't use cash anymore. Tap-to-pay, buy now, pay later, Venmo -- it's frictionless. And that's the problem.

According to a recent survey from the Federal Reserve, nearly 50% of Americans live paycheck to paycheck. And for many, credit cards fill the gap. But that leads to a cycle of interest charges, minimum payments, and financial stress.

Want to go further? Pair Buffett's habit with a high-yield savings account

Here's something I've learned from years of writing about personal finance: Small behavior changes matter a lot more when your money has a safe, steady place to grow.

If you're committing to a cash-based system to avoid debt, the next smart move is to stash your extra savings in a high-yield savings account (HYSA). Top accounts right now are offering up to 4.40% APY, which is more than 10 times the national average.

This one habit could change your financial future

Buffett doesn't live on a budget spreadsheet. He lives by a mindset: Don't spend what you don't have.

It's a low-effort way to stay debt-free, and it's just as effective now as it was when he started decades ago. If you're tired of feeling like money is always tight, this one change could help you take back control -- without sacrificing the things you care about most.

And if you're ready to put your extra savings to work, a high-yield account is one of the easiest wins out there.