What kind and how many miners are we talking about ?
I'm running Antminer U1/U2s for a total of 20 GH/s. Been running them since February and have paid for them already since I don't pay for power in my apartment.
How much coin do they produce?
About 0.011 a month given 100% uptime. I got them all very cheap from eBay.
I started out with those and then quickly got 3+TH miners which I just sold off. Don't think I broke even in the end but it was a lot of fun. Learned a ton of new skills at the same time.
Should have kept those U2 miners as conversation pieces.