Could you point me to an example fake granite slab that can be used in the shower, maybe from one of the big box stores?

Any of the big box store stuff will be able to be kicked in pretty easily if someone is determined. 

https://www.biggerpockets.com/store/house-hacking-ultimate

@Tom MatousekAdditional savings hack: Depending on if you bleed blue or orange, start at the second closest store you want to buy from, take their bid to the competitor then take that second bid to the closest store you want to work with.

Scott in the BiggerPockets book store. 

They don’t even ask.. so if they live like pigs, they aren’t going to change that for a $50 gift card to the local grocery store.

But if your unit has unpainted woodwork, or light switches, or outlets or carpeting or another type of flooring, or ceiling light fixtures, be prepared for a stupid mess when a very nice tenant becomes a very amateur painter.The above doesn't even mention the materials the tenant will use--sorry, but Walmart or Ollie's Closeout Store discount paint is not Sherwin Williams or Benjamin Moore. 

This is regarding a small retail property I own, it is a three store building.

If you go to a shoe store looking only for Lebron shoes, you are unknowingly willing to pay a premium over any other similar pair of shoes.

Try a local flooring store and see what they offer...