You don't buy a Masternode. You buy 1000 coins at an exchange and then you build a masternode following this guide:
https://github.com/coin2fly/coin2flycore/wiki/Masternode-Setup-Guide
Best,
Coin2Fly
https://github.com/coin2fly/coin2flycore/wiki/Masternode-Setup-Guide
Best,
Coin2Fly
Build it? I'm no computer scientists.. this will be to difficult for me