It's kind of sweet that

Though there was an opportunity for world-building, his old man version could have hinted that they get some kind of "commission" for hooking up new people to the Substance.

Sweet? It’s a precursor to what’s in store for Elizabeth. This very attractive male nurse (the one who introduces her to the “activator”) also turns into a decrepit aged person. So, it looks like no matter what, one of the two parties to this so-call fountain of youth project seems to opt out of following instructions. The doom is inevitable. Elizabeth sees for the first time in that coffee shop what is going to happen to her and the horror of it all. It’s very Dorian Gray. It’s not that aging is ugly but the way and why they aged that made them incredibly hideous.