Private Investigator/ Investigation

There is a very suspicious character who is attempting to lure my sister into marriage and he is very sketchy. They met online three weeks ago and he is planning to propose to her, he has told her he is rich, and sent her some money, etc. But now he is asking for money from her to help him out. It sounds just like a scam but I can't find much information on the guy, so I need help with at least getting more information on him, or people who know him to see who he is.