You only need a little income to invest. Even a small amount of income can be seen as an investment if you have the mindset to invest.
As far as bitcoin investment is concerned, you need a source of income that will allow you to have discretionary income after you have sorted out your daily expenses so that you will have the money to invest in bitcoin in such a way that it will not stop you from sorting out your daily expenses, which might get you off the game partially or permanently.
You are right, we need to have a source of income that allows us to have discretionary income however if we have a job that don't allow us to have a discretionary income we need to backup with a side hustle, some people who are working and still don't have a discretionary income is not because there salary is not good enough is because they have a bigger responsibility more than a normal human should have, they carry unnecessary responsibilities for example always sending money to there friends weekly or monthly as soon as there salary is being paid, there are some responsibility we should cut off.
Very good, to invest in Bitcoin every day you definitely need to have a fixed source of income. We can keep a remaining part of our daily income for investing in Bitcoin, which will reduce the suffering of investing, and how to increase daily income will lead us to find more sources of income. Since not all people are considered equal, some earn more and some earn less, so I think more income or less income is not the main thing. Patience and humanistic thinking are important for investing in Bitcoin in the long term. People with low income have more unwanted work due to their low qualifications, so they cannot join the investment field due to time and financial problems despite their desire. It is necessary to create their freedom by removing this unwanted responsibility from the lower ones by the superior officer, so that they can also use a part of their earned income and use their time and remaining money for investing in Bitcoin. Maybe their salary is daily, weekly or monthly.