Be lucky.<p>I don't mean to be flippant, but given the constraints, your speed will be almost entirely proportional to luck/risk.<p>To start, all you have is labor to bootstrap with. So let's say for round numbers $10 / hour, at 40 hours per week is $400. or $1600 for one month. That puts you six "doublings" away from $100K after one month.<p>Go to Vegas, bet it all on black (or red, your choice) and win 6 times in a row, and done. 1 month of labor + a few minutes of very lucky gambling. Or, a single bet that pays off 62.5 to 1. While the odds are the same it probably seems more "practical" to win "just" two 8:1 bets back to back.<p>Investments, options tradings, sports betting, etc will all be some variation of this. Get really lucky, and it can be done in a short time, but with a high risk that you have to start over, and it ends up taking a longer time overall.<p>More realistically, if OP can put all that labor money into investment/savings (assume subsistence is supported otherwise) The standard advice to buy and hold low/no- fee index funds could do it in about 5 years (on average).<p><a href="https://www.investor.gov/financial-tools-calculators/calculators/compound-interest-calculator" rel="nofollow">https://www.investor.gov/financial-tools-calculators/calcula...</a><p>400 initial, $1600 / month, 5 years, assume 7% yearly growth +/- 2% variance.<p>Finally, OP says "zero financial investment" - but what other resources do they have? Perhaps the sunk cost of education or training or other skills. Then, their labor might be worth $100 / hour, instead of $10. Get a high-paying job.<p>Then you could make it in 6 months of straight labor income without risk of investment or gambling losses.<p>All the above is wildly speculative, and not investment advice, and somewhat US-centric, and contains completely implausible numbers and assumptions, but is an honest attempt to quantify an answer to the question.