To be safe, get two Bitcoins.
lol i agree with this. in 20 years 2 bitcoin may be worth 2,000,000$ and to me a 2m retirement fund would last if you plan on retiring at 60 and living untill 75 or whatever. specially if you have another income coming in still from ssi or whatever it may be
safe side get 5
i dont think only assuming that bitcoin will rise in 20 years is a valid answer totally.
Reason:-
The above statement is only seen with positive point of view.You have left the negative point in it
Below is a chart showing bitcoin price drop and price rise
So i dont think going down with positive point only matters,you have to check negative points too.
Thats why users get in Trading.
example:- Suppose he bought a 1 BTC in 2014 when price was around $ 400(assumption) and bitcoin prices drop to $250 in 2015 is it profitable for
a retired man?
OFFCOURSE NO!!!
You have to play with market then,which you can do it through Trading