If your financial condition is that you already have children and a wife, then the appropriate amount for you to invest is the amount remaining after the family's needs are met.
If you and your wife have income, then arrange it by having a discussion with your wife to determine how much will be allocated for Bitcoin investment.

Profitable investment lies in the type of long-term investment that is carried out regularly every month.
Because the crypto market is very volatile, don't worry when prices experience a price drop like what happened yesterday.