Then apply them equally to everyone. Another method of avoiding even the hint of illegal discrimination is to think or every potential tenant as a potential customer and every tenant as a customer. Your current tenants are paying you thousands of dollars a year, paying your mortgage, property taxes and insurance. And potential tenants are eager to do the same thing. Thinking of it that way could well give an entirely different slant on your relationship with your tenant and potential tenants.
Fair housing is the right thing to do.