That's not really related to my point, which was that your definition of slavery is a non sequitur.
Of course, technically you're right - there will always exist a minority of people who were so wealthy (and lucky) that, even though they didn't care about wealth preservation, their wealth didn't run out before they died. If, in addition, these people inherited all their wealth (as opposed to doing any work to obtain it), then they are the (only) non-slaves by your definition, proving that not EVERYONE is a slave.