It is not good to borrow and invest in bitcoin even though you have an income because it will reduce your income based on the interest rate attached to it. Why are you in a rush when you can buy bitcoin whenever you get paid. This is why the DCA method is there to help us buy bitcoin with the little amount of money from our discretionary income.
I only borrow money from friends families and relatives that will not add any interest rate so that it will not be a problem for me when paying back, that is if I see a dip and I want to benefit from it. Sometimes I meet my Boss at work and collect salary advance which I can use to buy bitcoin at that moment and it will be deducted from my salary bit by bit. Bitcoin price is unpredictable and borrowing to buy bitcoin might put one in regret later.
Sometimes there are some conditions where you see an opportunity but you don't have the money you can use, for example when the market is dumping, then taking out a loan with a low interest rate is a good step to buy bitcoin (since not everyone has a good boss/relative they can lend to, like your case). It's just a matter of how someone can calculate their ability to pay and how they manage their finances, because anyway in the next month they will buy bitcoin, so buying in advance using debt is not a problem. And discussing the interest, if it is still very low, I think that if you expect bitcoin profits in the future, it is not a big problem, for example, a loan of 100 USD with 5% interest, that's only 5 USD in interest, but with that 100 USD you could get more profit in bitcoin. It's just a matter of debt management skills, and many bitcoin investors have done this.