Savings Account: 1,000 Yen Per Year

Deposit 100 million yen (about $700,000) in a regular savings account at 0.001% annual interest. The yearly interest is 100,000,000 × 0.001% = 1,000 yen. After roughly 20% tax, you take home about 800 yen. Forget a Mercedes - that will not even cover a tank of gas. 100 million yen in a savings account earns you about 5 cans of coffee per year in interest.

Time Deposit: 100,000 Yen Per Year

A time deposit (assuming 0.1% interest) yields 100,000,000 × 0.1% = 100,000 yen per year. After tax, about 80,000 yen - roughly 6,700 yen per month. Enough to cover a phone bill, but nowhere near a Mercedes payment. A Mercedes C-Class (about 7 million yen) would take 87 years of interest to buy.

Index Fund at 5%: 5 Million Yen Per Year

Invest 100 million yen in an index fund returning 5% annually. The yearly return is 5 million yen. After tax, about 4 million yen - roughly 330,000 yen per month. At that rate, you could buy a Mercedes C-Class in about a year and a half. Even an S-Class (about 15 million yen) in under 4 years. "Buying a Mercedes with interest" is genuinely possible with an index fund.

However, index funds carry the risk of losing principal. A 5% return is a long-term average; in any given year you might see -20% or +30%. Your 100 million yen could temporarily drop to 80 million. "Living off interest" requires the mental fortitude to ride out volatility and the cushion of several years' living expenses held in cash.books on building passive income cover realistic strategies for living off dividends and interest.

Building the 100 Million Yen Comes First

The "Mercedes from interest" dream is fun, but first you need 100 million yen. Investing 50,000 yen per month at 5% annual returns, it takes about 47 years to reach 100 million. At 100,000 yen per month, about 35 years. At 200,000 yen per month, about 25 years. The numbers are daunting, but with compound interest they are not impossible. The key is to hold the goal of "living off interest" in mind while putting every possible yen into the compounding cycle starting today. The Mercedes is waiting at the finish line.