A teenage scam artist uncovers a money-laundering plot that euthanizes seniors and cons an army of old people to extract restitution from the mob.

I agree with Paul, my old addition would be to add a flaw to your main character. Such as why is he a scam artist, personal issues? and what are the stakes for him getting involved?
otherwise it sounds really interesting. Also curious about the genre?

I think the logline, and title, are excellent! Great job, and a movie I'd be interested in at least reading (read my mission statement @ www.sharkeatingman.com(Shark-Eating Man Productions).

Sounds intriguing. What does the teenager get out of it? Why would he risk getting involved with the mob?

Otherwise, a very strong logline. Good dramatic irony in that he is a scam artist, but uses his skills as a con man for good. I can already see his character arc. A clear inciting incident, and clear goal. No stakes are mentioned, but I guess if the mob is involved, it's pretty obvious.

I like it.