Look for signs of water damage, like stains or discoloration on walls.Roof problems are also common.

What's behind that door, in the garage, how's the mechanicals look, is their water stains anywhere on the ceiling, etc. 

Sam, Have you opened the ceiling where the leak stain is? 

The great part is very little siding, staining, painting. 

With this said, I would never do this for a rental so this is a rental (tenant moved out) that I plan on selling using a 1031 exchange on soon and the garage floor has lots of cracks and stains so I want to make the floor look nicer.  

I have them all replaced. 2. curtains/drapes are stained with food and whatever red, purple color. 3.

@Jason Staine I used my local credit union where I also have personal and business accounts. 

Does it cover water stains as well as they say it does--in one coat?

I need to buy a new shirt as I just spit out my coffee and have coffee stains all over it after reading this post.

Towels get used on the shoes, fancy cutlery goes missing, no one wipes their feet, wine stains...