Remember to use two factor authentication to provide an almost bulletproof security.

Michael Jordan and Nike.

IMHO the easiest and most definitive is for the owner and you get an authentic survey. 

Remember, people use Airbnb for not only a cheaper visit, but also a more authentic one.

You have to get out there and as nike would say "just do it".

@Allende Hernandez most RE professionals (realtors, home inspectors, etc) in our area use SUPRA (http://www.supraekey.com) which allows you to  authorize anyone who has a Supra FOB or their smartphone to authenticate.

Jude children's research hospital, Nike's world distribution plant, etc. 

I hear ya on who lives where.we have that same issue in our Market with Nike's 7k employees and Intel's 20k plus. 

., a mobile authentication company."

You then want to authentically acknowledge them by letting them know how smart they are and how much they already know about the opportunity that you are sharing with them.