The best way to take loan for Bitcoin investment is when you are working and you take a loan and then little percentage of your salary will be taken weekly or monthly till the loan is completed, if it is done this way then there won't be any problem, and for those who wants to take this move please Don't be in a hurry make sure the interest in the loan is okay one that won't affect your finance.
Honestly taking loan for bitcoin investment is not advisable. It makes investing meaningless when they become unable to pay the loan on the agreed date. It's always a risk though to borrow and invest in Bitcoin due to the price fluctuation. It also depends on where you take the loan and how much interest is giving. Bank loans are extremely high avoid them. Margin loans for stocks are typically around 5-6%, while property investment loans are closer to 3%. There's no reason to overpay when applying for a personal loan.