You’ll need insurance certificates (named insured), and there may be a union that thinks that you are invading their turf. In some respects it will seem like you are working for the GC.

I make a point of talking with the project supervisor or building engineer. Here I can assure the “boss” that I’m not a hazard and I can assess how anal the situation might be. I don’t usually have any trouble. I am about to start a job in a condo building and the customer warned me how disagreeable the building engineer could be. I scheduled a meeting with the engineer, we bonded, he was very cooperative, and I don’t expect any trouble.

I’m sure that these points have already been laid out for you, but there are structures that you will not be permitted to penetrate. The GC is not being mean. I’m sure that he knows the building codes better than you. In the job above, I was very concerned with this sort of issue, until I met with the engineer. (There could have been lead and asbestos abatement issues).

Will you need to tie-in to the building’s security? They may have a visitor gateway scheme. These can be very inconvenient, requiring the resident to use a special house phone. You probably will not be allowed to tie into this arrangement, but it always pays to ask.

Make sure that you have a reliable ground for the cable feed. (I like FIOS)

Edit: Some jurisdictions require a permit for low voltage wiring.