While this website provides an extreme example of the opportunity cost of raising a child in terms of stock market investing, it could have easily illustrated a negative extreme with a stock such as Lehman Brothers (delisted from the NYSE in 2008).
Generally it is not advisable to invest a whole portfolio into a single stock. Diversification is the key to a sustainable investment portfolio. While picking individual stocks can be fun (and produce outsized returns), beating the market is difficult to do. Most individual investors would be better off investing in indexed funds or ETFs. If you'd like to learn more about investing, we recommend you take a look at the two books that we would consider the gold standard of investing: The Intelligent Investor: The Definitive Book on Value Investing and A Random Walk down Wall Street. These books are displayed below.