Quantity   Component name
1 × Arduino clone per node Any Atmega328-based board will do, specially the $2 Pro Mini clones
1 × nRF24L01+ module per node The popular nRF24L01+ modules
1 × Battery or a 5V adapter PCBs from cheap USB wall chargers work well for powering a node
5 × Relays for light control Use any number of sensors and actuators you need
1 × A small linux board to be the server Use a $17 TP-Link router or a Raspberry PI or anything that runs python