I think the right time to borrow bitcoin is when you play a trade, and get the information that there is a coin that cost would be very high. maybe it can make us a profit
Yeah. Generally if I find a trading opporutnity that will yield me more than what the loan interest is, then I would go for the loan. Especially if the opportunity only lasts for a limited time.
It's also useful if you're wanting something immediately, instead of waiting for your pay and buying later.
It would be a nice move if you could invest it right away knowing that you can make profits out from it.