Property Owner Keeping Sale a Secret From PM.... For Now

[Tanner Pile]

I'm working with an owner to purchase a property off market. I have gotten a good amount of information to make an official offer. However, I wanted to view a unit or two that is vacant and check out the utility room before proceeding. Owner has a property manager that I could coordinate with but the owner does not want them to know they are possibly selling yet. 

Any tips on getting through this with the owner? or been in a similar situation?

I plan drive by and see the outside but I may need to run my numbers best I can with out seeing the interior and make an offer to get under contract and than make any adjustments during the inspection process. Thoughts??