The answers to your questions may be very simple, such as, Start investing with as much as you can afford to invest. If you have less amount of money then invest less amount and if you have more amount of money then invest more amount, Aim to invest consistently.
Many people invest by borrowing money from others. If one has a fixed source of income he can borrow money from others and invest but does not have to sell his investment. Because people don't always have money even if they have a job. So if he invests with a loan and later if he can repay the loan with the money he gets from his job at the end of the month, it means he can easily repay the money he borrowed from others. As a result, he no longer has to sell the investment to repay the loan.
No matter what it is not even advisable to take loan to invest in bitcoin. In bitcoin investment you must earn for you to be able to invest that is why it is an investment that one needs to have a source of income which you do not need to borrow. I think the only reason that would make one to borrow money to invest bitcoin is due to desperation, just to make money quick and when you depend in taking loan to invest bitcoin it is very possible that the investment won't last long. Loan for investment is stressful, it is better to get a source of income , no matter how small it maybe you can afford to invest with the amount you can afford and your investment will keep going smoothly.
In fact, investing in Bitcoin with debt is a really bad strategy, Bitcoin is unpredictable, and Bitcoin's movement is unpredictable, no one can give you any accurate direction on when and where Bitcoin will go. And the most important thing is that Bitcoin will never guarantee you a profit. So since there is no guarantee of your profit, how can you decide to invest in Bitcoin with debt?
You are taking a loan, that is, you must repay this loan with interest, now if you invest this loan money in Bitcoin, Bitcoin can cause more loss instead of giving you a profit. Because the movement of Bitcoin is unpredictable, it can decrease and increase at any time, so due to this unexpected movement, it may return you less money than the amount of the principal amount you invested in the future, because the value of Bitcoin may decrease at that time, (this is also possible). So how will you repay that loan with interest?
So you should definitely invest only that money, which even if lost, will not have a big impact on your life. And you must have a stable source of income, and invest a percentage of your income through DCA.
Taking loans in the hope of quick profits can often lead to bigger losses. "So not with loans", with patience and proper planning, buy DCA with the amount of money you can afford and decide to hold for a long time (at least 10 years). Only then can you get a lot of good from Bitcoin.