What if it's an office building?
Buy a real domain name and use that. It is probably cheaper than a single square foot of office space. (This can either be your normal domain name that you already have, using split DNS to make more things resolve on the internal network, or an entirely separate domain name, whichever is operationally easier for you.)
I bet many homes have more money for domain names than some shops/offices.
Just wondering why they didn't call it 'localnet' or some other unused synonym for local.