" Deviating from your written lease or policy indicates inconsistency, which may lead to an accusation of showing partiality, also a form of discrimination. For example, if your lease states that a late fee will be charged for any rent not paid by the 5th, and you enforce the late fee with one tenant (they’re kind of a jerk) and not another (you like them), the tenant charged the late fee may feel they were discriminated against because of another reason. Regardless of your reasoning (one tenant was nice and the other a jerk), that situation could quickly get out of hand. It’s best to simply practice consistency and stick to your written policies. "

― Brandon Turner , The Book on Managing Rental Properties: Find, Screen, and Manage Tenants With Fewer Headaches and Maximum Profits