Over the years we have seen a lot of crazy people, most of the normal human have no problem with common sense being good tenants, some are poor and have problem with the reality that not everything is perfect (i.e. home insulation is not perfect because it is an old house, refrigerator or stove is old because this is a mid range apartment not a luxury one). Most often if you explain to them they would understand, but there are always desperate people wanting more but not wanting to pay for it. It is important to screen tenants and look for signs of trouble and deter them from renting your place, and it is always important to price it slightly lower, not looking at your property with rose tinted glasses and wanting to charge what you "deserve", so you have a pool of candidates you can choose from and pick the most "normal" person. Most of the ones we picked end up saving enough money with their hard work and end up buying a home when they move out, I think we did pretty good on that. We do keep our duty of maintaining very seriously and we do repair everything, sometimes an old still functional appliance if they are starting to act funny but still functional, to keep them happy.
There are a lot of tenants who pay their rent on time but, shall I say hard to work with, even if they are paying on time and didn't destroy your property they curse at you like they are your boss, or complain about everything because they are entitled to quality of living in their mom's house when they are just renting an empty apartment. Usually when we have enough we would ask them to find a nicer apartment and we would let them end their lease early with no penalty, and most of the time they would immediately stop complaining. Emotional toll of managing these people all add up to something in the quality of life department. Most of these problem IMO attribute to people trying to rent too much housing with their too little paycheck. People who don't overstretch their budget tends to have fewer problems.
Iit is in all ethnicity and all walks of life, all income levels, all education level, all N genders. The most accurate predictor tends to be rent to income ratio and credit score.