What is the minimal hardware I could use ?
I cannot use my laptop any more, no more drive space, too slow when I work and I have to turn it off at night.
https://bitcointalksearch.org/topic/bitcoind-091-on-raspberrypi-633347
https://bitcointalksearch.org/topic/how-to-run-bitcoincore-010-on-raspberry-pi-2-981465
raspnode.com/diy.html
http://www.hardkernel.com/main/main.php
https://getaddr.bitnodes.io/hardware/
However the argument is, if you're actually helping the network with such a low spec computer, as it is slow with the tx forwarding (IIRC).
Yes that's the thing : there is no point of running a slow node.
It needs to be fast and effective.