Locking gate around unit areas, that works well and can't be snuck through or unlocked from outside.

You do not need a realtor for anything other than to unlock and lock the door and submit an offer.

It is quit nice having a separate scheduled code for each guest / tenant.The other lock / wifi hub app only allows me to lock and unlock the bolt remotely.

Even if something bad does happen, I'm so far money ahead on this strategy I'm never going back to the old method of dropping everything to run over to a place and unlock it just so people can text me 15 minutes after their appointment, "Sorry, but we're not coming...." 

Renters call me, I give them the address and leave the door unlocked with keys on the kitchen table. 

This may be repeating what they told you, but perhaps not:Has the manager checked to see if the door is unlocked and keys may have been left in the mailbox or inside the property, visible through a window?

Or is there the assumption that the door is already unlocked?

First day of ad somebody called, told them the particulars, and the address, and told them to show it to themselves that the door was unlocked.

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If you wish to install a click lock on upper stories look into a recommended acoustical pad to deaden the sound; thin , dense so as not to cause the product to unlock if walked on.