I just took some old pc's I had and pulled the 12vdc ans out of em, got 2 fans outta 2 pc's, had to rip open the power supplies on them, but four fans I would never use, I found a 12vdc power supply in a junk drawer, it was for a usb hub, rated three amps, each fan pulls about 1/3rd of an amp thats about nine fans possible
on one power supply, wiring is really easy, just 2 maybe 3 wires red black, and sometimes and on one of mine white, black is negative red positive, if you get them backwards the fan just blows backwards, pretty straight forward and easy, hard to mess it up