Retirement plans like 401(k)s and IRAs play a significant role in accumulating wealth, particularly for those who start saving and investing early in their careers. The average 401(k) plan balance for individuals aged 55-64 is $408,420, which can significantly contribute to achieving millionaire status. Proper asset allocation and portfolio management can also aid in achieving millionaire status. Diversification in investments – stocks, bonds, and alternative investments like real estate – can form a well-rounded portfolio for financial planning.