I usually post it on the door. tape it over the lock and then I know it's been received because they have to take it before unlocking the door to enter the unit.  

I'm sure there are a few people out their laughing because they've unlocked that puzzle and will keep silent.

If there is a tenant in place, I will wait until there is a turnover unless there is a common door that needs rekeying also.I now purchase all of my locks from landlordlocks.com and if I ever do need to rekey a property after a moveout, it takes about 30 seconds to do so and I can easily reuse the lock on a different property.You'll also get a master key that will unlock everything and anytime you order a new lock, it will be keyed so that your master will work on it.

But I do have tenants that work very odd schedules (I'm in a town with a couple Auto Manufactures) So tenants are not always home and I have to meet my guys there to unlock.

For instance, they need to go unlock a house for someone who wants to go back a second time and do some measurements, they give you the keys and you do it.  

You will save thousands in commission, you did all the work, why share a huge chunk of your profit with someone who just unlocks the door and shows people around?

I'm looking in to Reonomy right now. seems like they can unlock some true owner contact information. 

In essence, they're basically saying there's a certain sequence of steps to follow that, if done correctly, magically unlocks this pot of financing which the banking industry or creditors will not tell you about. 

and what do you personally look for when unlocking hidden value?

Luckily, I didn't have work and was able to arrive within the hour and unlock his unit for him.