If you have the mindset to invest, you can invest in two ways. Those who have stable cash can invest easily without any hassle; on the other hand, those who do not have any savings can also invest. 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.
Bitcoin is not a stable coin, but a volatile assest.
Those who don't have discretionary income cannot invest in bitcoin, because with your little income without any discretionary income will be for your daily needs and not to invest, otherwise, you will sell your bitcoin at loss when the need for the money arises and bitcoin price is below your entry point. You can look for a second meas of income or trim down your expenses and invest in bitcoin with the funds from your second meand of income or from the funds that you realized after triming down your expenses.