I don't know why the both of you are complicating things for yourselves. But let me try and explain this as simple as I can so you guys can get something right. When an investor get his salary and he removes all the money for family necessities, what he have left is called discretionary income. From that discretionary income he can remove a portion of it to build his emergency funds and his reserved funds. Then he can invest the rest in bitcoin. As times goes on, if the investor sees an opportunity in the market and his salary hasn't come and he doesn't want to miss such an opportunity, he can take money from his reserved funds account to invest in bitcoin and build it back gradually. So yes an investor can buy bitcoin with money from his reserved funds account.
The distinction between discretionary, emergency, and reserved funds is worth mentioning. Risk management emergency or backup funds must never be pegged on such a volatile asset as Bitcoin. It would be rational to use discretionary income or a small part of the saved money as you indicated, but novices must realize the risk of putting a hand on anything that is intended to be applied to necessities. Throughout history, numerous investors who considered all the savings as a form of disposable income found themselves in trouble at low times. Invest only what you can do without it not to have any impact on your day to day life.
You are using too many grammar here, and it is very possible you can complicate things for yourself and also for newbie because of wrong placement of those grammar. What do you mean by risk management emergency? Is there anything like risk management emergency in Bitcoin? Use word and terms you are familiar with and stop using words that will contradict what you are saying. You made a valid point, an investor is expected to use what they can afford to let go but what you can afford to let go doesn't mean small amount of money but rather it depend on your capacity and cash flow and also your discretionary.