If the original owner does "Erase All Content and Settings" before turning it over to you, that automatically turns off Find My iPhone and Activation Lock. There's no need to ask for ID and password.
The issue with this is getting 15 employees to all adhere to this. And in situations where the phone is taken in as loan collateral erasing the content is not desired.
If the phone is not picked up I take ownership of the phone. A lot of the time the customer does not want to cooperate after the fact with giving me their login because they could not afford to get their phone back.
At this point, iPhones taken in on loan I need their Apple login information.