We need discretionary income to invest in Bitcoin. So if we say that we should not invest using business money, it will not be completely correct. Currently, there are many big companies whose main purpose is to invest in Bitcoin. So if we invest our money with the right plan, we can invest any money.

But, I agree with @op to some extent. Among new investors, there are many investors who cannot manage money properly for investment. They become very aggressive while investing. They invest all the money at once without any future plan. Later, when they face financial crisis, the only way is to sell the investment, which is the worst moment for an investor. Therefore, we should do business with proper planning rather than using business money. In this, we can continue investing in the long term using the return money we get.

Otherwise, which money you use to invest is completely your personal choice.