Fuck-you money means you can walk away from a shitty situation. You can fire an annoying client. You can turn down offers that conflict with your values, or are just plain boring. You can call out any shady behavior in your company or industry, instead of being held hostage by a comfortable salary.
Let’s define fuck-you money as the amount of cash you need to feel a basic sense of security. Say, one or two years’ worth of living expenses—enough to walk away from a bum situation, turn down any gig, or re-train for a new career.