score:6
While there's always an inherent possible risk with these types of sites (VBRO, AirBnb, even hostel websites) - for the most part, they work fine - otherwise they wouldn't work!
Always look at any reviews on the property/owner - if any, and see if there have been any noted problems in the past.
Perhaps Google the address or property as well, just to make sure it is where it says it is. If there's a phone number, you could call to double check on some aspects - what's included, and so on.
However, if you're really paranoid, or cautious - say, if you've just put down $1000 on a rental, you could consider their VBRO Guarantee, where from $39, they'll cover you for up to $10,000 in fraud, misrepresentation or even just a double-booking.