Leak, who patches? 

Hello,I had a partly damaged wooden floor in one of my rentals five years ago but I did not do a good job back then  hiring the right contractor as I was a noob and back then they installed prefinished flooring with completely contrasting very dark flooring stain, also while they ripped  of the flooring in the room they applied it as a patch  in one of the sections in living room where the flooring was damaged. 

I understand you can buy older water heaters as replacements, but this one would be on its last legs in a few years..4) Found a small patch of mold behind the kitchen sink..been there before and is an immediate red flag. 

In less than an hour the roof is stripped, bad spots patched and papered.

If there's not much water going down the line and the bill is higher than around $40 per lot then it's probably main line leaks.To fix main line leaks you need to walk on top of your water line and see if there are any marshes or patches of greener and taller grass -- signs of water leaks.

Or, patch it in with Sheetrock compound which may crack later too.

I require tenants to wife down walls, remove all nails/screws from the wall and patch all holes.

My new daily to-do list - Fix leaky toilet, patch wall, show property, document tenant sex, cut grass. 

I put in new kitchen flooring, patched a few walls and cleaned up the front of the house with new shutters, paint and landscaping.

It sounds like you are headed in the right direction after a rough patch.