I really, really wouldn't recommend buying DASH now, but if you want to do it, this isn't the best way.
You should go to an altcoin exchange, the biggest of which is Poloniex. Buying from people will only get you scammed, unless you're a scammer yourself, in which case you won't have a lot of luck here.
Uhh ok thanks for the heads up
Why would you not recommend if I may ask?