About the time my wife, Valerie, was in college, reasonably safe 6-month certificates of deposit were averaging roughly 11% a year, quite enough return for most folks. That train has left the station! Lately, 6-month CDs offer income of only 0.5% or less.
Suppose you or a child is going to be at the university and won't have time to work while engaged in studies. Or maybe you expect to be retired one day, yet your job doesn't provide much (or any) pension. For a number of reasons a significant, regular dollar stream can be just what is wanted and needed. So what is one to do for income today?
It is more complicated now, and higher returns are not so available as in, say, 1983. Yet it definitely is not "mission impossible."
For a really safe stash of cash, funds one can count on for a few months in an emergency, it still pays (for security plus a tiny bit of income) to invest in money market accounts (MMAs), for instance, FDRXX (0.01%).
Short-term bond funds, like BSV (1.51%), are almost as reliable as MMAs and offer a little more return.