Hey there I'm a newbie and I was just wondering say I have 7  antminer S5 machines ...and free electricity would it be a worthy investment and how long would it take to pay off?

Hi I am a newbie to the forum but I have been researching bitcoins for a quite a while now just haven't had the capital to really get into it.i began by using faucets but can now see it is a waste of time.on that note I would like know the most viable and trustworthy Bitcoin investment sites?