The biggest mistake one will make is taken a loan to pay back when Bitcoin goes up in Price, when you do this it will lead you to dip your has into that same Bitcoin investment you borrowed for to pay back.
And yeah you are correct JaaJuanGee if one has a good source of income then there's nothing wrong in taken a loan.
I love the questions you put forth and that should be what we should think of before getting into taken a loan to invest on Bitcoin if one has a clear vision then the loan will be of help, I know of someone that always take loan when ever an emergency or problem has eaten up all his emergency, reserves and float funds instead of dipping into his Bitcoin investment his working and receives good salary so it those not affect him and he always pays back the loan and that has really helped his growth in his Bitcoin.
I think this issue of borrowing to invest in bitcoin have been adequately dealt with in this forum and majority of participants already know that it is not a good practice. This is the reason emphasis have always been laid on investing with ones income and even setting aside emergency funds after settling basic needs. With borrowed money, it becomes difficult to even think about setting aside emergency funds because the debtor does not have enough money or is going about his means to be invested in bitcoin so there is bound to be pressure on him on both personal needs and from the creditors.
With borrowed money, the investor will be increasing in debts on the interest of the loan and even if the investment yields profits, such profits will be used to settle the interest in the debt and it is worse when the investment is not yielding instant profit like the case of bear market. This is a terrible experience every investor must avoid. The disadvantages of borrowing money to invest in bitcoin as just too many.