I work in a company which rents a floor in a large downtown office tower and I think the number of people working there is less than 10 including cleaning staff. There is 1 security guard who I see around often and someone is usually in the management office and at the end of the day a pair of janitors come around.

I've also visited WeWork offices before and you're right that they have a lot of extra employees. They usually have multiple people at the front desk checking people in, then there are people who are going around to make sure the kegs are full and the shared spaces haven't detoriated into pigstys (this is different from a typical office where Janitors come around once a day or sometimes less than that).

Do not forget that you need about 5 employees to fill a single 24/24 365/365 work position. About 3 for a 2x8 position.