The answers that will appear will definitely be many different but i think that cryptocurrencies can certainly be used as a source of income, but you have to have other sources of income to avoid losing liquidity, regarding whether it is good to buy crypto with borrowed money, actually it is legal, as long as you are able to pay each installment or you have a stable source of income that can cover the installments then continue because cryptocurrencies, especially bitcoin, have become a safe haven.