Even after I was rich, I wasn't one to sit around twiddling my groins.
So I spoke once more with Thomas Edison, again at knifepoint, and he told me electricity was the new thing!
Thereupon I invested in coal power, hydro power, girl power, and finally, nuclear power...
...secretly running the plant myself until I was old enough to actually run it myself.
Ah yes, I remember it well.
No, wait, I remember it poorly. But it makes sense.
I grew very old and very rich. Then, in desperation, I bought the Youthenizer from myself, paying a sum vastly higher than I'd dared imagine as a lad. It was enough to pay off the loan and turn a tremendous profit to boot!