no, never. It is too risky and wrong idea to borrow money to buy bitcoin or any investment asses such as stocks or commodities. These market is full of risk and there is a possibility to lose money. If you are not rich enough to invest, the best thing you will do is not to invest. You should get a job and find money, not borrow it.
I think different if you already have a lot of knowledge and have the skills to invest/trade in bitcoin, because the risks on the bitcoin market and borrowing money can be tolerated with the skills you have of course you can get a profit easily and pay off the debt with your profits. that's why there are many lending sites in bitcoin world included on the exchange site.