I am not sure what you can tell someone that will have any solid outcome. When I was a teenager, I was already fired up about saving, investing, buying vs. renting, income streams, etc. And then... life happened, and bit by bit I drifted away from that until I was paying 1/4 of my pay every week just to extend the due date on pay-day loans until next week... when I'd pay another chunk of money to extend them again...
Then I got a better paying job, ditched the loans, and started it all over again with credit cards. Hundreds of dollars a week went down the drain paying interest and penalties on stuff I had bought months ago. I couldn't even remember what the debt was for, but I still had to cut a check to pay off just enough to get by until the next month. Anytime I made some headway on our debt, an "emergency" would come up, and we would promptly max out all of our credit again.
Why did it happen? It's not because I lost the desire to have money! It's not because I had a head injury and forgot how to do compound interest calculations or how to work out a savings plan on an Excel spreadsheet. It happened because, somewhere down the line, I decided that I was a worthless person who had to buy the affection of others or risk being alone for all my life.
Deep down, I always knew it was the wrong thing to do, but that just reinforced my negative outlook - after all, who but a REAL screwup keeps doing something wrong when he knows better? That HAS to be the sign of a loser... so I guess I better keep paying for all this stuff I can't afford to distract people from just how big a loser I am...
It was impossible to say "no" to people. What if they didn't like me? What if she left me? What if...? What if...?
Despite all my hard earned knowledge from my teenage years, gathered from reading investment books and making an almost fanatic study of internet sites like this one, I ultimately failed to put any of it to effective use.
So, knowledge doesn't always do much good, no matter how much of it you have or how early in your life it comes to you. You have to have the strength to use it, too, and not fall into the cycle of self-defeat that other people, who have no cares about the future, will do their best to drag you into.