I've been running Apache Spark/Hadoop on six RPI 2 for about three months so far, and it serves me quite well. The cluster is a bit more of investment than six instances of cloud node, but it runs deadly quiet and works quite well. On top of that, it runs on Raspberry PI for God's sake!
You can start running Apache Spark/Hadoop cluster with two RPI 2, and one PC with following items.
Oracle Java 8