Almost nothing.
Even giving you a generous 50kH per machine @ 50 machines, that's only 2.5MH.
With free power, that's a whopping 0.82502930 LTC or 3.32$ USD over 30 days.
Keep in mind, that's running the machines full bore or close. If you think you are going to have these miners running in the background, not messing with the main functions of the machine, well then, you might want to have dad re-think the plan.