All the reasons you have mentioned are all correct, if you don't have a Discretionary income you shouldn't even think about investing in Bitcoin because if you use money that is meant for basic needs to accumulate Bitcoin then you will be in a big financial problem and you will even end up dipping hands into your Bitcoin investment there by interrupting your accumulation journey.
So before going into Bitcoin investment you need to have an income that after handling basic needs with it you will still be left with a Discretionary income no matter how small it is, you can use a small amount of your Discretionary income to invest in Bitcoin and succeed but you can't use basic needs money for Bitcoin investment and succeed.