DCA is an effective strategy, it has a high probability of producing positive results in the long run, but there is no guarantee. Bitcoin is an investment that, if managed correctly, can have high long-term potential, but it is never guaranteed, and for this reason, you should not invest money that you cannot afford to lose, here you have to invest with the excess of your income, that is, you have to invest only that money that you do not need, no matter how small it is. There is no guarantee here, so investing with debt is never a good decision, so you should not lend him money, but rather advise him to invest with money that he can afford to lose.