I see that you don't understand the meaning of discretionary income and that's why you feel that one discretionary income is not important before you can invest into bitcoin. Whether you have a stable source of income or not, you need to have a discretionary income from you stable source of income or unstable source of income before you can start up your bitcoin invest. Discretionary income is the extra money that is left, after you must have taken care of your monthly expenses and basic needs. It's that extra funds that you need to invest with. Some people use this extra cash to do whatever they want but it's wise to put yours into bitcoin weekly/monthly overtime.
However, an investor needs to wait for his next discretionary income in other for him to continue his bitcoin accumulation if he has already used the one that he has at that moment.
There are many that don't understand what discretionary income is before entering into bitcoin investment and this is wrong since it is advisable to invest using our discretionary income.
Discretionary income is the money that we have left after sorting out all our expenses like food, house rent, school fees etc.
So discretionary income is what we should invest into bitcoin to have a stress free investment. Regardless of whether we are earning high we shouldn't invest more than our discretionary income and this is after we have sort out our expenses.