Generally, taking a loan to start up a business or invest is not a good idea because of the added pressure it comes with. It's more better to use a loan money to finance an existing business and the interest rate must be very low, so that while paying it back in instalment, the business or investment wouldn't have to feel much effect from it.
But as of the case of Bitcoin investment, it's a bad idea because Bitcoin is an asset that should be held in a very long time, so thinking of paying back the loan with the money invested in Bitcoin is one of the worst thing a Bitcoin investor should do, because he might be forced to sell at a loss or prematurely just to pay back when the loan debt is due, so taking of loan with the purpose of investing it in Bitcoin is one thing we should all avoid, because it's not proper.
Actually its not actually a bad idea since how could you fund your business if you didn't take a loan to make it happen? Its just you making all of things work according to what you like to happen. If you scared enough to do this then could you get a result for having that feeling? For sure not. In Bitcoin I think its the same if you could pay back the lender why not? You are not trading it, but rather you are investing it for long term so with that set up I think everything is fine.
As long as you know what you do is good and you are capable enough to pay your loans then there's nothing wrong with it. The time it became a wrong decision to take, if you know for yourself that you cannot pay your loans but you still decide to get it and used since you will would really get a big problem with that especially by the time that the lender will ask the money what you lend to him/her.
you may be right or correct but either ways i do not still buy the idea of going to loan money to invest in bitcoin even though we are doing it for something that is really promising and has a great potential and also, regardless of the source of income i still do not actually buy the idea because anything is possible and human being are full of surprises and wonders and since bitcoin investment is not running that is to say that we can invest anything we have... just that we will missed some great opportunity but it does not matter, so it is best not to loan money but rather wait till you are been paid and then continue because sometime payment can be delayed or put on hold because of one thing or the other and again the person one loan's money from can have a challenge and he or she may be tempted to ask you for the money back and the way some people can be aggressive you won't have a choice and what if your investment is still in loss...