Billy and Akaisha Kaderli retired in 1991 at the age of 38.

The couple, now 68, have watched their nest egg grow from $500,000 to more than $1 million, while still managing to fund their lifestyle.

The strategy they use is pretty simple: Track every dollar you spend, and invest in index funds and ETFs.

Check out this video to learn more about the five budgeting techniques these retirees use to grow their money.

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