A sublease is an agreement where someone takes over part or all of an existing lease. This type of lease involves at least three parties.Sub-letting is somewhat market based. Is it illegal to sublease a room in a house against the terms of a lease agreement? If so, can I sue or report this as a crime? Some state tenant laws say you're allowed to sublet if your lease allows it. So, re-read your lease. If you leave your apartment or other rental home before your lease ends, your landlord must make a good-faith effort to fill the vacancy. In a sublease, the landlord only collects rent from the original tenant, and the sublessee's rent obligations are paid to the original tenant. Definitely. In New York, at least, if a landlord "unreasonably" withholds consent for a sublet or lease assignment, the tenant can break the lease.