you must have an alternative source of income by which your bitcoin investment can only be fertilexbti yield profits when you invested and doesn't panic it to grow else he may end up selling his bitcoin at lost having me to be blamed.
the dividends of his bitcoin assets would had be reliable to him after much he may have made some profits from it.
This is not about alternative source of income, but how much money he can set aside to invest which will not affect his monthly spending, this is why people who want to invest something need to have emergency funds.
If he only have one job that pay really well, he don't have to looking for alternative source of income.
Bitcoin never produce any dividend, if Bitcoin can produce dividend or generate more coins, it's clear you're hold your coins in centralized exchanges, holding in CEX is bad for security.
That's just it, I agree to your sentiment bro, you don't practically need another source of income for you to be able to invest in Bitcoin, what is actually mandatory is having a source of income that comes in regularly then I believe that you are good to go, because as long as you are paid weekly or monthly, the logical thing to do is to invest an amount you can do away without through the DCA accumulating strategy, with that, you can still sort out your monthly expenses, so with that method it would be must more easier to invest, as long as it's an amount you can do away without.
So I would advice that your cousin to first of all look for a job, then after that, depending on how much he is being paid, he would have to remove like 10% or 15 % from it as long as it's an amount he can do away without, with that, I believe that he can start his accumulating journey till he is quite ok with the stash of Bitcoin in his possession.