Avoid ending up like a friend, who used all the money he has to invest in bitcoin and also took a loan, promising the lender that he will pay back when he gets paid in a month, after a month he never received the salary, I warned him doing this, because he has no doubt mixed investment with 'whatever it takes', is it safe to call this greed? I don't know.
Now he wants me to lend him some money to at least pay the loaner back and later settle me, there is more, now I have to send him some money to buy some food.
You don't have to use all your money to invest, even if you are not married yet or have other responsibilities, the best approach when planning to invest in Bitcoin is to buy with some percentage of the money you earning, maybe through business or a job.
If you do this weekly or monthly you won't feel any pressure, always remember that health is wealth.
In the first place, you dont have to let your greed motivate you into investing. Investing has its own risks, so one should never invest with greed to the extent of investing all your life savings, or taking some loans just to invest. Those were a big NO in all types of investments. I just hope your friend is aware about this before he starts to invest. Now, he is facing the consequences of his dumb decision, and its up to you if you will help him or you will try to let him suffer the results of his own greediness.
One investment I knew that can trigger greed that much and it is a Ponzi Scheme investment. Just like what the earlier reply stated, it is possible that his friend is a victim of a ponzi scam. Maybe his friend is promised a good return monthly so his friend, seeing how huge will be the possible profit decided to go all in even getting a loan to add more fund into the investment then the ponzi company run with the money.
It is a good thing to help a friend in need @OP. I hope your friend had learned his lesson well and will recover quickly. It has been advised that we must only invest the money we can afford to lose, is free and is not committed to any obligations in order for us to have no problem if the investment goes southward.