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I'm 18. How to build good monthly income at my 20's?
It looks like you need a lot more education on the subject. I suggest you pick up a book on investing and portfolio management to get a first idea. Dividend yields are currently way below 5% on blue chips. Unlike coupons from fixed income instruments (which, in the same risk category, pay a lot less), dividend yields are not guaranteed and neither is the invested principal amount.  In either case, your calculation is far away from reality.  Sure, there are investments (such as the mentioned direct investments in companies or housings in emerging economies) that can potentially earn you two digit percentage returns. Just remember: risk always goes both ways. A higher earning potential means higher loss potential. Also, a direct investment is a lot less liquid than an investment on a publicly quoted high turnover market place. If you suddenly need money, you really don't want to be pressed to sell real estate in an emerging market (keyword: bid ask spread). My advice: the money that you can set aside for the long term (10 years plus), invest it in stock ETFs, globally. Everything else should be invested in bond funds or even deposits, depending on when you will need the access. As others have pointed out, consider getting professional advice.