Jika yang ditanyakan adalah bagaimana Warren Buffet mendapatkan uang untuk berinvestasi, sejak kecil ia sudah bekerja part time sebagai paper route (pengantar koran)

Tetapi jika yang ditanyakan bagaimana ia bisa berinvestasi di umur yang sangat muda, itu karena bursa saham di Amerika tidak memerlukan ID/KTP untuk berinvestasi di bursa

1. There is no citizenship requirement for owning stocks of American companies. While U.S. investment securities are regulated by U.S. law, there are no specific provisions that forbid individuals who are not citizens of the
2. U.S. from participating in the U.S. stock market. https://www.investopedia.com/ask/answers/05/foreignownershipusstocks.asp#%3A~%3Atext%3DThere%20is%20no%20citizenship%20requirement%2Cin%20the%20U.S.%20stock%20market.
3. As long as you have a Social Security number or Individual Taxpayer Identification Number, you can buy and sell stocks online – even if you’re a nonpermanent resident or a noncitizen.

Are Noncitizens and Nonpermanent Residents Allowed to Buy Stocks Online?
As long as you have a Social Security number or Individual Taxpayer Identification Number, you can buy and sell stocks online – even if you’re a nonpermanent resident or a noncitizen. According to the Department of Homeland Security, noncitizens can usually get an SSN if they’re legally in the U.S. and authorized to …

https://finance.zacks.com/noncitizens-nonpermanent-residents-allowed-buy-stocks-online-11588.html#:~:text=As%20long%20as%20you%20have,nonpermanent%20resident%20or%20a%20noncitizen.

Di Indonesia memang diperlukan KTP untuk berinvestasi di bursa saham, saya sendiri sudah berinvestasi di umur 15 tahun menggunakan KTP orang tua (tentunya dengan izin)