This isn’t the building being a CB but is generally expected appropriate behavior in buildings with staff. The magazines in cities like Bew Tork provide advice on what is considered to be standard. You tip just as you tip waiters , delivery people, taxi drivers , manicurists, stylists and similar and there are normal minimum amounts. Restaurants with a high number of foreigners dining will often include something on the menu or charge a service fee. I live in a full service building and my holiday gifts to staff probably were close to $2000 and we do pay staff well as well as provide with health insurance.