i've also built small rubbermaid DWC units in witch you can put 6 plants, for a cost of 40$.( 1. dual outlet pump=15$, small ruberrmaid storage container=5$,
2 12 inch airstones=10$, 6 two inch netpots=6$, 3ft of tubbing=2.99$)

and you got yourself a easy to use small hydroponic system for under 50$, if you are really concerned about stealth spend a few extra bucks on a whisper air dual outlet pump witch runs almost silent, compared to my 15$ petcetera pump.