Anyone can join to invest in crypto currencies, but does the person ready to lost the money, since the elder already living with retirement money it is better to stay away from risky investments, crypto currencies is a very risky investment, if you see the chart the price movement is really wild
You are right, It's risky to invest in cryptocurrencies, because you don't know when a cryptocurrency increase or decrease, you should depend on your point of view of market. By the way, I don't think that is too late to invest in cryptocurrencies for elder, because they can even make a huge profit in 5-10 years later.