Living with someone shows you who they are faster than ten years of hanging out. Pick roommates carefully.

Hanging out samples somebody at their best, on purpose, a few hours at a time. Sharing a space samples the unedited version: what they do at two in the morning, how they behave when money is short, whether they clean up when nobody thanked them last time. Years of friendship can leave you completely unprepared for that, because friendship never asked for it. The information arrives fast and is not always good news.

Before agreeing to live with anyone, ask the boring questions out loud. Money, guests, noise, dishes, what happens when rent is short. Twenty awkward minutes now saves a year of resentment.