I am southern California born and raised all my life, I've traveled around the country, some of the world, and recently lived near Phoenix, AZ for the easy part of six months before the heat.

electric Baseboard heat.  

A nuisance complaint about a barking dog that turned into a heated argument and then a fist fight.

It's 3bedroom 3 bath 2 1/2 car heated garage, 1 acre land, has probably 1800+ upstairs sq feet downstairs is finished with 2 additional bedrooms / with closets another 1800+ sq feet.  

There property currently has in window cooling units and no heating source.

The meters are not separated but I was wondering if there are any rules in SC regarding charging back for electric, heat, and water?

As an example, when I buy a unit, I do all of my heavy capital expenditures up front - heating, roof, etc - which leaves me with minimal capital & maintenance costs going down the road.

In other words, if they rent from someone else they'll be asking grandpa for money to pay that rent.Hopefully they will abide by your request not to work with grandpa any further but I suspect that since grandpa and grandma are in South Carolina and you're in Georgia, these tenants might continue to hit up grandpa for these things same as before.One has to bring up the issue with aging relatives....is grandpa able to continue handling his finances or is he at risk (as my partners mother was from Bills brother) of being taken advantage financially due to changes secondary to elderly dementia issues?

There are only a very few items that you may need to have someone go pretty quick, usually heat or water. 

The current heating system is an oil fired steam boiler and radiators.