I know an older acquaintance with 20 billion won............................

I know an older acquaintance who received 20 billion won through inheritance.
He doesn't do any stock or real estate investing at all;
he just keeps it all as cash in his bank account.
He says that if you mess up with stocks or real estate, your life is ruined,
and that keeping cash is always the safest way. Is he right?
He says people who trade stocks are no different from gamblers,
and that investing in buildings is a foolish thing to do.
What do you veterans here think?