Bitcoin investment is not always good to borrow money for its investment, but one can choose to borrow sometimes depending on the situation of things at that particular time. Business is full of risk, likewise investment, and bitcoin investment is just like any other investments which are open to risk. So, if one can borrow money for other investments, there is nothing wrong with making such trial. l think the most important thing is being very careful, and knowing a lot about bitcoin, and its record, and then know exactly the right time to make such investment.
The truth of the matter is that it's not always advisable to borrow money to invest in Bitcoin, but if you must do so, let it be done in a calculated manner, like taking a calculated risk.
First of all you kill that notion that you will be paying it back from your Bitcoin investment, because if you are actually borrowing money to invest in Bitcoin, the loan must be a loan that will be repaid back installmentally and spread across three to five years interval, so you can easily pay back that loan from your paycheck once it arrives.
And to buttress it all, if you took the loan to buy a dip, their is a higher probability that Bitcoin will always outdo any interest attached to the loan, so it's not a bad idea entirely to invest in Bitcoin with a borrowed money if you are paying it back from another source, and it's done installmentally.