I have a great solution for that. Buy about 50 cheap phones, and set one in the middle of the building with wifi Hotspot enabled. Spread the rest of the phones around the building, and keep the closest ones connected to the center device. Turn wifi Hotspot on those devices, and they’ll retransmit the wifi from the center phone outwards. Do this until all phones are connected to other phones, and you’ve got a cheap and horrible mesh wifi solution with 50 SSIDs