I'll try to respond to as much of the stuff in this thread as possible.
FIRST. Jorge Cervantes needs to fire his editor, and fast. His Indoor Grow Bible is so full of typos, misprints, etc that it gives me anxiety just trying to read the stupid thing and I HATE it. Is is an okay guide for nOObs, yeah, it's fine but take it with a grain of salt... Argue with Jorge... lol sure any day!
I keep my flower room humidity below 40%... I shoot for the 30s.
The concept of relative humidity is one that you can use to your advantage... with increased temps, the air can hold more moisture. If you find yourself in a situation in which your humidity is high and your night temps are significantly lower than your day temps, you can end up with actual DEWFALL after lights out!
There are options for dealing with this.
FIRST your ventilation has to be very good... you need an active exhaust to carry warm moist air away from your grow area. That by itself is likely to solve your problems... plus the problem that isn't quite so obvious, which is that with insufficient ventilation your yield is going to suffer, mold aside.
Next, consider adding a space heater on a timer to go on about a half hour after the lights go off when the room starts to lose heat. This will eliminate any dewfall problems you are having.
Oh yeah.. computer fans... no computer fans!! they are just not sufficient for most growing applications. Get down to walmart and pick up a few of those little metal high velocity fans for $5 each... they move some serious air for their size.
Dehumidifier not in the budget... well in the words of someone around here... go cheap, grow cheap. This isn;t a cheap hobby. Skimping on equipment will not save you anything. REALLY.