Pro-rated is pretty common. 

By taking steps to minimize your exposure to risk, you can avoid large, costly errors that will cause you the biggest headaches.

He misidentified mailing address as property address, and however many cards were in that same batch all suffered the same error, if not all time.If you are running a business with infinite upside and potential life altering downside, take the time to make sure your data is right. 

Would it make sense to get some sort of error or workmans comp or some sort of insurance? 

Also make sure they have Errors and Omissions insurance. 

I also plan on installing key phob entry for the lobby, and some security cameras in the common areas to better secure the property and help the tenants feel safe.  

The biggerpockets.com people paid some lawyers to write up reasonable leases: https://www.biggerpockets.com/landlord-forms I've only looked at the California ones, but that one had not only leases, but common addenda, applications for the tenants, etc, and both PDF and Word docs that allow you to edit if you wish.

(Then there is of course the follow-up questions- Other than yard maint/snow, garbage, utilities, etc. anything that's commonly missed that I can put on the Sched E?)  

Is that common for your area?

It requires common sense, like everything in life.