Dear Dave: My brother and I recently received an inheritance after our mom died. He's never been very good with money, so I was proud of him when he used his portion to pay off his debts. But then he went out and financed a $23,000 van he can't afford. I'm afraid he's falling right back into the same old money problems, but I don't know how to talk to him about it.
Over the years I've learned that you can't make people listen to you. Even with what I do for a living I don't throw my opinion around unless someone asks.
I'm glad you realize there are some boundaries here. Still, there's no reason you can't create a situation where he can ask your opinion. You might begin with talking about some of the mistakes you've made in the past. This could help him connect with you and feel more comfortable opening up about his own situation. Once he realizes you've learned from your mistakes and haven't repeated them, he might feel comfortable enough to ask how you accomplished it all. Then, once he does that, the door is open!
But you can't become preachy or act like a know-it-all every time someone does something dumb. Acting that way makes you seem arrogant, and you'll probably only succeed in hurting the other person's feelings and making them tune you out completely.