>Did they earn their living by working? Then they are working class. If you make a salary or a wage, if you have a boss, you are working class.
There's a pretty massive gulf between a heavy equipment operator who's making token contributions to retirement and would have a tough time with the mortgage if his spouse lost their job and a brain surgeon with maxed out retirement accounts, kids at ivy leagues and a vacation cottage on an exclusive lake.
They might work 500yd from each other but they are not the came classes of people. The arcs of their lives from birth to death are wildly different. Both depend on their wage to sustain their lifestyle. But the doctors (and the other people in their neighborhood) mostly wouldn't be caught dead living the way the heavy equipment operator lives (and the reverse is only slightly less true).
Referring to the latter working class is something usually only done before telling the former they need to stop drinking bud light, driving 30 cars, get the project boat out of the yard, vote a certain way, talk a certain way, etc, etc you catch the drift.
Working class carries a very strong implication of blue collar work or not significantly more than blue collar amounts of money. A social worker or paralegal is working class. An investment banker or law firm partner should find other words to use.