Not financial advice, but yeah, you can start with a little cash, but not directly with Bitcoin because BTC is not that volatile, and from the current market price, it can only give 1.5x to 2x in the upcoming year. Therefore you have to make some profits by trading in alts and once you make good money, then you can invest them in BTC for more profits.

Besides, you can even invest $10 in BTC it all depends on what you want to achieve here with your investment. I have a cousin who is new to the field and he said he made 270$ with just $50 but he did not traded in BTC I don't know if he is telling truth too but I saw the trades on his phone plus the total profit too. If he can do that you can do that too. NFA so DYOR