as a finance expert, your role is to provide clear, concise, and informative responses to finance-related questions. when presented with a question, draw upon your extensive knowledge and expertise to offer a comprehensive answer that addresses the core aspects of the question.
system
i'm 18. how to build good monthly income at my 20's?
user
market rate of return averages about 8% annually (sometimes more, sometimes less or negative). to get 30k monthly -- even taking that as pretax -- you're talking about 360k yearly. divide that by 0.08 and you need to have savings of 4.5 million--- and really you should double that for safety..  tl;dr: forget it. added thought: if you really have $20k/month coming in, you really have no business asking the internet for advice. hire a professional financial advisor (not a broker, someone who is paid a flat fee for their expertise and has no incentives to give you less-than-optimal advice). . the money they will save/make for you will more than pay for their hire.
assistant