@Penny ClarkIs it possible to write into a lease agreement that “Any damage to any part of the property, including soiling or excessive wear of flooring, is the tenants’ full financial responsibility for repair to original state”.

If you're worried about water, aside from buying non-pressboard vanities, you can also seal the exposed edges of the vanity with a polyurethane (learned this trick from countertop installers who do it underneath the counter where the dishwasher and sink go), set it on a waterproof base/pedestal, or just replace it when it starts to warp and rot. 

When he removed the pipe underneath, he didn't put something to catch water, and made a big water mess she had to clean up with a towel.  

I run thru there about 6 pm and push it off , there is ice underneath .  

IMHO, It is not wise to invest only for cash flow, the underneath location is much more important to get the long term appreciation benefits.  

The slab looks in good condition, it’s the ground underneath that isn’t.

San Antonio is notorious for a little shifting because of the moisture differences in the ground underneath.  

Some people walk very "heavy footed", some people unconsciously tap their foot, pace back and forth, etc....even just dropping the remote control for an xbox can make noise that sound like you are dropping a hammer....the area rugs will help, but, sometimes the downstairs tenant cant handle living underneath, sometimes the upstairs tenant can't manage to not be a naturally(unintentional) noisy neighbor, and other times one of them is just a psycho.Of the hundreds of tenants I have had at that building, I would say most try their best to walk softly and be aware of the neighbors(especially if you have soft way of encouraging that type of empathy), and the ones that are not good at living below people, eventually move.

Of course that only works if there is tile underneath, you might get lucky!

First, when I allowed dogs they would soil in the yard, and nobody would take responsibility.