Khaled,
Well, I feel bad because I can't help you. And, you will probably hate my advice again. I guess the negotiation is over, but I would still go back and ask. I do think you are making it way too complicated, and think there will be glitches; not to be negative.
Personally, and I am rather secure with my network, I have no problem leaving computers where others use the same space. Granted, I would not really want them sitting at the same exact desktop where my computer is (and I freaked out when my new cleaning person moved the computer three feet to clean).
How about this. It's crazy but who knows. Do you know of any other office adjacent to yours you could put the server it? Then run a cable through the wall. The downside would be access.
The person you are leasing from has computers. He/She has to know you need them. Think of what you need and tell them what you need to work there.
