We don’t rent to smokers, so not an issue. 

You would be surprised how many people sue their landlords  because of the 3, 4th, 5th, 6th, 7th, and 8 second hand smokers affect their health and anyone that touches the door knobs.

Then use Pinterest for ideas on the looks of ideas of fire pits, grills, picnic table(s), games (horseshoes, volleyball, etc)...

Quick Question:  Do you all allow grills at your SFR rentals? 

(They have the deferred maintenance you'd expect after a fixed income senior lived in them for several years, plus smokers, pets)So how do I turn 5 straggling houses into a proper real estate portfolio and well-managed rental business? 

Pending how bad the staining - i.e. how long the smoker was resident.  

Are they just "smokers" or drug addicts?

One of my LTR tenants is a heavy marijuana smoker and the smell is invading my Airbnb.

Adding some artwork to help give the place more character - $100-200 on Etsy or Society6 can get you some really unique prints that will help your apartments show well in listing pics and really set them apart from the competition.If you have the space outdoors, the quickest and easiest amenities to add are a fire pit and BBQ grill (or maybe a patio as well, if you're so inclined). 

A George Foreman grill a family pack of chicken breast and frozen vegetables go a long way. it has to become a priority that you are willing to forgo convienances for.