Roommates. They're a fact of life for many young people who want to live in the heart of major cities across the country, with what rents are nowadays. But what many don't know is that they may be breaking the law.As explained in a recent article in the New York Times, several areas, including-surprisingly-New York City, have laws against allowing more than three unrelated people sharing a residence. Though these laws aren't strictly enforced-or rather, are rarely enforced-it may still be a concern for landlords.Say these laws are enforced. Who would be held responsible? The landlord? The tenants? The apartment manager? What would happen to rental rates? And how about apartments in college towns, where it's not unheard of to have several people living in a single unit.If you're an apartment owner or manager, are cohabitation laws a top-of-mind concern? Are there ways to get around them? Has anyone had to deal with these issues in reality? Are they a detriment to muiltifamily owners and operators? Or do these laws make sense?