The purpose is to have a financial buffer to rely on in case of unexpected emergencies or hardships.

I would stay away from smaller buildings, even if they have tax abatements, because unexpected capex can be crippling among fewer owners, and smaller buildings can more easily fall out of Fannie Mae compliance.

How much cash/financial reserves on hand do you recommend I have for unexpected expenses (building: 50k-60k sq/ft, 10-12 commercial grade HVAC's, building is about 36 years old)?  

The TV shows fail to show the bankroll behind the deal, the number of contractors working when the camera is not rolling and the issues that invariably come up on a flip that were unexpected.  

After job completion, he mentioned that one of the electrical outlets in the kitchen wasn't working right.  

New foundation (unexpected), new floors, new kitchen, new bathroom, new porch, new electrical, plumbing.

Unfortunately, my sister died unexpectedly a couple of weeks ago and our family is in NH. 

When you figure that one out let me know.

But I wondering if I should just patch it and leave electrical outlets only?  

I recommend Building Material Outlet in phoenix as they have the best price that I have found for materials.