I purchased a Home in SC as a second home and the taxes are through the roof.  

I would recommend finding an investor friendly agent in the area you are wanting to invest to be your boots on the ground.

The purchase decision might make itself clearer once you are here, have boots on the ground and are not pressured to make a decision from long distance.

This is my first time and I'm buying a fixer upper that needs a new compressor, roof and a total kitchen remodel.

Water penetration can also include roof failures or pipe bursts that allow water to leak into or damage your home.Either have the repaired area researched by your local expert and accept it.

New drywall, mechanicals, windows, electrical, roof, siding- essentially new from foundation up. 

Or just avoid ST booking platforms.2) Converting the roof into a terrace (apt. on the top floor).

And take the roof off and build up.

The worst experience we've had was with a flat roofer (very common roof type in Chicago) we finally wrapped up, after waiting almost two years for them to finish/fix something. 

What's the life expectancy of the roof, paint, furnaces, water heaters, etc.?