Then you also need to consider smoke and water damage.  

Complaints of new roommates coming in "out of nowhere" (it makes sense because the owner has to rent the room), people smoking pot (good luck proving who make the living room couch smell like weed and *just* evicting them), and just a ton of complaints.  

Nonetheless, they"re smoking.

That being said, as a flooring professional, I wouldn't have carpet anywhere in a rental other than a bedroom and only if there's no pets or smoking.

The City fire marshal has an annual inspection where we load new batteries in the CO/Smoke detectors and replace the fire extinguishers.  

On the inside it is easy to tell kids would come in and hang out and get wild as there were dozens of liquor bottles and cigarette butts strewn throughout all the units.The carpet was horrendously stained with God knows what but luckily it didn't smell as bad as it could've thanks to no windows :) Holes in all the drywall and most faucet heads missing.

Two years ago the fire next door left a good amount of smoke damage.

I have a no drinking and no smoking policy on my job site, you will be off with a warning the first time, but termination on second if within a year.

I cosmetically renovated the lower unit due to messy tenants that smoked heavily and apparently never owned a vacuum for 5 years.

We had the carpets shampooed twice, cut the grass and found a year's worth of dog poop and cigarette butts, and scrubbed the garage so it didn't smell like smoke.