It's 67% for break even before you consider your hand, but bear in mind that sometimes your cheeky steal actually hits a flop. Your hand has equity, so factor that in against villain's calling range to get a more accurate idea. If you're confident you can play against the BB close to optimally post flop, then you should be able to show a profit against some people who fold to steal <60%, but I tend to target those who are >60% (until they adjust, of course) to play it safe.