I've grown and cultivated carnivorous plants for years, and I'll tell you, they are the PICKIEST plants. They have to have the right amount of sun, the right soil, the right temperatures, the right humidity, the right water. I have to to grow mine in temperature and humidity controlled aquariums and give them specially treated water because regular tap water will kill them.
They also honestly don't eat as much as people think they do. A venous fly trap will simply open again if it doesn't need the fly and release it.
There is no way you could grow or keep enough to actually manage a fly problem.
Though for anybody who loves challenging plants, I heartily recommend growing them for pleasure! They are extremely fun and beautiful. My handle "Ibicella" is short for "Ibicella Lutae" which is the scientific name for a semi-carnivorous southwestern plant called the "Devil's Claw."