Not every investment gives your an opportunity to start with a small capital.. things like real estate, stock like you mentioned m, requires a large amount of capital to begins and your profit or let's say your RoI would be like in a couple of years which is true..
I agree with you, there are some investment that you going to need a big capital for, not all investment you going to tell me that you can start small. Just imagine you having like $100-$1000 to invest, how will you be investing little amounts like that in real estate, that’s not really possible, so if your plan is to invest in real estate, then you should have sure you have a big capital, because you won’t be able to make the investment with small capital.
If you are talking about small capital, then you can invest in crypto, and other investment. Even if you have $10 you can still invest it in crypto, you can decide to buy bitcoin or other coins with it, when investing in crypto space, then you don’t really need so much money before you will be able to achieve that. You can even start investing gradually, you don’t have to buy the coin which you are planning to buy at once, so you can just make use of DCA strategy and invest. I will say thats one of the advantages of bitcoin, you don’t have to be rich before you can buy bitcoin.