It was stained and old, but the reason I am replacing it is because it got wet and has some mold.  

Elite Tier pricing, usually reserved for The Home Depot customers after spending $100k in a year, unlocks meaningful discounts on renovation and maintenance materials.Save Up to 20% on Paints, Stains, and Liquids: Save up to 20% on paints, stains, and other liquid products from The Home Depot's extensive selection.

They are a crisper and don't set stains as easily.

For example, they wanted new tile in the bathroom, its an older unit, so the grout is a little stained.

Ceiling stains, which can indicate leaks from above.9.

Today as I was staining some trim boards in the back of one of my rentals, I see a man in a uniform standing in the yard looking at the house.

Even if you do paint/stain it, you need to make sure it is clean before doing anything-preparation is everything.Not sure how well paint would stick to those surfaces or wear. 

I would check for water stains on the ceilings and leaks around the windows as well as soft spots on the floors.

Probably a light sanding, a coat of stain, and about 3 coats of clear will make them shine!

The upside of that is when they move out (because you won't be renewing their lease), if there are ANY stains; you can bill them 100% of the cost for that carpet because it was brand new when they lived there (okay maybe not 100% as it will be a few months old when they move out, but 95%).