They also pay you thousands of dollars a year in rent and make a profit for you. Your responsibility is to provide these folks with a great place to live. If you rent to a bad tenant, you are telling the other people who rent from you, the good tenants, that you don't value them as customers, especially if you own a plex or an apartment building. Bad tenants are the people who don't pay the rent, who disturb their neighbors, who trash and place and who consider a good place to live one where they can get into whatever mischief they want without interference from their landlord. In fact, they consider landlords to be an infringement on their freedom and their right to be general, all-around bad citizens.
Bad tenants leave such a smelly trail that even a landlord with a sinus infection can follow it.
Create rental standards and stick to them. Just setting up basic rental standards will go a long way toward ensuring that you keep bad tenants at bay. Four items must be on your rental standards even if nothing else is. These will eliminate the worst of the worst before you have to worry about income, rental history, credit and other qualifications. The rental application must be completely filled out.