Right on Robert..my first clue would be the request of such a large Down payment. That's a Big chunk of Denero to trust you will recieve the goods.I would call them innovators, entrepreneurs. Lone wolf, anti-establishment, independent...could be perceived as good traits...as well as bad traits too. Trick is to see the red flags and know when to walk away.
I think the good advice was already shared here about not plunking down your cash before the delivery of your truck mount. Seems safe and reasonable to me.