If you'd started 35 years ago you could have had a decent quality of life earning a living as a mailman. If you're starting out now you'll probably need a second job to make ends meet if you're in an expensive part of the country..
Entry level mail carrier makes an average of $35k. It goes up to $55k after 20 years. That's around $17.50 to $27.50 per hour. That's not wealth, but it isn't poverty either.
My grandfather raised a family of eight kids on a mail carrier salary in Walla Walla after he got back from WW2. He sent them to private catholic school as well, I really don’t get how he did that.