I guess I have a little advantage as I can look up who owns the home and some other details. The best filter mechanism is to simply ask the poster the name of the company they work for and the contact info. Then ask them a few questions about referrals and references.
Out of the 9 leads my friend sent me all 9 of them were scams and they all were like you mentioned, asking for a western union or moneygram payment upfront.
