My new locksmith try to convence me to install those system on one of my unit and might be others as he explaint to me I keep one key for all units as master key.

I wonder what would happen if you 'broke' in (got a locksmith to change the locks) while they were out and said the same thing? 

They could take that lease and sign it and show up and get a locksmith and move in. 

(Don’t go this route, not worth it) I then decided to talk to my local locksmith and they are able to give me high-quality Schlage locks and they can key a master key and they can also key individual tenant keys.

Locksmiths for locks.

Anyways, the attorney tells me we need to have a locksmith there to change the lock.

If I am unable to get to the property, the tenant will be charged for a locksmith, but under no circumstances are they to remove screens or try to break into windows.  

I received a quote for $500 from a locksmith and I think its a little expensive.

Then I would show up with a locksmith and change the locks.

Also have a locksmith present when the cash for keys occurs.