If you aren't handy with carpentry (as I suspect you aren't since you are asking how to build a cabinet).... then I suggest you go to the Salvation Army or Goodwill.... you can get furniture at those places C*H*E*A*P! Look for an old dresser or hutch of some sort.
Screw in hooks to the top to hang lights from and use a 6" circle saw (the kind they use to create the holes for recessed lighting) and drill intake and outake holes to move air with fans.
Hope that helps
EDIT: At my goodwill Tuesday is 1/2 off furniture day.... call yours and see if they have a similar discount day for furniture and then shop on that day. You could end up paying $10 or $15 bucks for the cabinet.