I think everyone could agree that if you run your butt off, and go thru the mechanics of running a business with all the work that entails in itself, if you are left with nothing after paying all your expenses, you might as well have enjoyed your days sitting in a park under a tree or something, for the same zero money.
And it's true, you would hate to think of yourself reaching an age where you want (or need to for medical reasons) to slow down and retire, and find you have nothing to live on, or even in.
I don't think anyone is saying a set certain amount is required in order to be considered 'successful', the obvious is just being pointed out, in that if you end your month, year, or life, with zilch, then how successful were you? Better to think about it now, than later, when it's too late!
In another thread, people are talking about running an average of 2500 miles per week.. so things can't be THAT bad out there, there should be plenty to pay oneself an income and save for future days!
Pretty well all companies require a DOT physical as part of their company requirements, and it seems most also require a CDL, even for a van.