This is a fairly common scam that people run. They advertise the horse as being super well broke and bred for such a low price. The only problem is that they require you to send them the money and a money order for transport before they will send you the horse. Then they take the money and run cause there is no horse.
There are a lot of Friesian scams out there. From what I've read, there are probably more ads for Friesians that are scams than are legitimate. There are several other threads about this on the forum. If it sounds to good to be true, it probably is.
They kinda remind me of those emails I get (several per day on my work account) for lottery winnings or inheritances with all of the goofy grammar.