No rent payment? No say in how this house is run.

Parents often use old sayings to rationalize their authority over rebellious teenagers in the house. My house, my rules, right? It’s simple to digest, doesn’t yield any room for argument, and firmly sets a parent’s jurisdiction over the household. They’re paying the electrical bill at the end of every month; bill-paying adults should be able to complain about lights being left on in the other room, the thermostat’s overly hot temperature, and a wide-open fridge door. 

When you’re the one paying the bills in the house, it should be clear that you have the final say in how things are run. Don’t like it? Move out. This is often an empty threat when it comes to parenting, but when it comes to a live-in relative with no concept of autonomy, things at the family dinner table start to get a little more complicated and a lot more passive-aggressive.