You actually can't do this.
A buddy of mine found a few buildings which have some offices which had some vacant rooms which were like $100/month.
They included power, heat, lighting, AC, etc. However when asked about how much power they can supply they said you can't just put miners in there which will end up costing more money in electricity then they will make profit from rent.
If you are going to be there 8 hours a day working, then you can probably hide them somewhere but leaving them unattended with all the noise, will bring up suspicion.
Not all charge more for electricity though. They figure you will have a few comuters, maybe tv/projector. And heating/cooling and lights. They don't expect thousands of watts of gear to show up. So a lot of leases it's ok to do if they were lucky, but chances are the lease also gives owner a way to kick you out pretty easy... which miners would cause.
Also most offices are not set up for a ton of miners. The wiring and breakers and such just are not designed for a large amount of electricity I don't think.
