This is just the end point of it, when using a borrowed money to invest in Bitcoin you don't plan on paying back from the profit you make from your holdings, you pay back from another source, that's why I made it very clearly that if the loan is being payed back installmentally from your paycheck it's quite cool, especially if the interest is on the lower side and it's spread out across three to five years payment, but if the interest is high and you planned on paying it back from your holdings, it's a no no in my own opinion, because it's a terrible mistake to be making in this age and time.
Personally I don't support the idea of someone borrowing to invest in Bitcoin, I totally discourage such mindset, Bitcoin is not like other investment so it won't be nice for anyone to borrow to invest in Bitcoin, it isn't right for me, mate there are some investment we can actually borrow to invest in but not Bitcoin unless an investor has a good source of income he or she can lay hands on later to pay up the loan just as you said but whats they need of even doing that, instead of borrowing when you have other source to pay back, why not use that same source to keep investing slowly consistently, I don't support borrowing to invest in Bitcoin, Bitcoin investment should be done in such a way that an investor wouldn't put him or herself in an unnecessary pressure that's capable of making his BP to rise, since we understand and know that we can actually invest in Bitcoin with what we can afford temporarily and increase our level of investment when your income comes up, I don't see any need of doing otherwise for no just cause when we can do things gradually,steadily and relaxed without being bothered.
Borrowing money to finance a bitcoin investment might sound unpalatable to you, and it is normal for you to feel that way due to the fact that bitcoin is a long-term investment and the borrower might not depend on his bitcoin investment to repay his loan. In my opinion, if the borrower has checked the terms and conditions of the loan and he seems okay with it and knows he can repay back the loan with his source of income before the due date reaches without him taking profits from his bitcoin investment or without him selling any of his property to repay back the loan, I think it is okay and fine for someone to take a loan to invest in bitcoin.