A person does not need a large source of income to invest. A person can start investing only if they have a reasonable income. Because it is very important to keep your investment consistent because if your investment is not consistent then you can fall far behind the goal of building your portfolio.
What an individual needs to invest in Bitcoin effectively is a discretionary income, you don't necessarily need to we earn much before you can start your Bitcoin accumulation journey, irrespective of how much you earn, once you are able to sort out your discretionary income you can easily invest in Bitcoin and be successful in it if you can be able put in place all the necessary measures that will make you to be successful, like having an emergency funds and a reserve funds to up your investment.