As a young investors you don't need a million dollar before you investing I Bitcoin, you can start by investing $200,$300,$500 everyday for 2 or 3 years, and you'll be a millionaire, and I know today that is how most people start up there Bitcoin investment journey and today they are millionaires, so that is also a way for the young investors to start their investment journey, thank you.
$10 a day is enough, IMO. But we need to add more years for it to see a significant increase in the price of Bitcoin, probably three to four cycles of continuous DCA-ing of $10 every day is enough to give us a good profit and probably can earn us millions of dollar if Bitcoin price keeps on repeating the history of recording ATH every 4 years
In calculation assuming BTC only raise around an average of 4x every cycle, that would be a whooping 256x (4 x 4 x 4 x 4) of our initial cycle investment. So with $10 for 4 years would give us $14,600 worth of BTC investment and multiplying it with 256x is equivalent to $3.7m+ return for 4 cycles (16 years).
While in your given calculation that amount of $200-$500 investment is pretty much heavy for a normal employee and thus is a bit non-realistic to attain. Plus in 2 to 3 years, if the person starts investing now might end up in an even return since two years from now, the BTC market will possibly transitioned to bear market and price might probably slightly higher than the current price or worst might be lower.
In investment planning, the timing should be taken into account, so the length of holding and selling should be carefully planned so that the moment we plan on selling our holdings will align to a bullish market.