The point is "mainstream" medicine... if you want to call it medicine.
It's easy. Find young and old with the same blood type. Screen the young blood for diseases. Inform the old that the screening will not ever be perfect, and that the young blood might cause some changes in the old person's thinking and attitude... besides youthfulness. Suck out the blood from the young, and inject it into the old.
If government makes trouble for you, set up a private membership association (PMA), and do the process with all the medical safeguards in place that you can think of.
I forgot one little thing. Transfer the money to the kid.
BTW, if the kid is underage, get a firm voluntary, signed statement from him, where he understands what is going on... and understand your rights as "owners" of your property, the underage kid. (DuckDuckGo search on "Karl Lentz common law.")