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.
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 means of income or from the funds that you realized after triming down your expenses.
I think Wonder Work knows that bitcoin is not a stable coin, but what he was trying to say is that those investors who have stable cash or stable income can easily invest in bitcoin without finding it difficult to do because their stable income will allow them to comfortably invest in bitcoin and also allow them to sort out their daily expenses anytime they arise, which will also allow them to hold their bitcoin for a long time.
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.