OP, your friend has great plans for his future and how he's preparing for his retirement.
But the question is, how can he do it consistently with 20% of his salary every month? It's hard for me, of course.
I can imagine that it is difficult to stay consistent with 20% of his total salary, with a journey of 16 years it is not a short one but on the way everything will not go smoothly according to plan, there are always urgent needs every month.
You have to see how much salary you get and what your lifestyle is. Everyone will not be disturbed if they do not have dependents every month and the salary they have is only used for themselves, not for other important needs. For those who have many dependents every month and have to pay for the needs of their wife and children, it will be difficult. setting aside just 10% of the salary is quite a lot, but sometimes there is nothing that can be set aside due to emergency needs. Buying bitcoins every month consistently with money set aside for salary is a good idea, but needs adjustments to all conditions. If it's consistently done it's the same as connecting, but with Bitcoin investments that have the opportunity to go up and provide benefits.
How much salary and lifestyle is of course that is a factor plus if they are already married and have children who are already in school of course the dependents will be even greater, usually the basic monthly salary will be very limited if someone who already has dependents in them will paying more each month for settled needs.
Emergency money must also be prepared in times of urgency so that an emergency fund will be our savior in an urgent situation.
I know that everyone, even though they are married, has a frugal lifestyle plus a large monthly salary, for example, of course they can set aside a little for bitcoin, if their salary is above $1500 I think they invest a little in bitcoin.