A few random ramblings worth approx 2% of a dollar
About 30% of the population are smokers. But, if you examine the upper and lower socioeconomics, the rates are very different. Much less than 30 % of high income earners are regular smokers, but more than 30% (I think it is about 45%) of people on social security are smokers. Also, the amount smoked by each is vastly different. Again, the low income earners smoke significantly more each day than high income earners. (After all, if you are on the dole, you have plenty of time to get through 2 packs of winnie blues a day, but if you are a high income earner {particularly if you are dealing with clients/general public}, it is very hard to be a heavy smoker)
Interestingly, smoking is actually beneficial (in the short term) for depression and some psychiatric diseases like schizophrenia. Thus, when depressed schizophrenics try to give up the smokes, they often need an increase in medication.
The heavy smokers are also disproportianately affected by alcohol and other drugs (particulartly cannibis). ps did a bit of a research project in high school- all smokers had tried cannabis at some stage, whereas it was a much lower % in the non smokers.
So, if you try to screen out smokers, you will also have a smaller chance of renting to people with mental health, drug and alcohol and social problems.