From Residential Landlord Tenant Law in N.Y. § 2:44.
Andrew Scherer
§2:44. Restrictions on occupancy/roommates may be unlawful—Roommate can only be charged proportionate share of rent for rent stabilized apartments
Charging a roommate rent in excess of his or her proportionate share of the rent can be the basis of a cause of action for actual, but not treble, damages under the Rent Stabilization Code. See, e.g., Bryant v. Carey, 196 Misc. 2d 412, 765 N.Y.S.2d 146 (N.Y. City Civ. Ct. 2003).
Should the tenant refund the roommate the overcharge, however, that roommate may not be able to establish a prima facie case of profiteering. See, e.g., L.E.S.P.M.H.A., Inc. v. Nunez, 12/18/2002 N.Y.L.J. 23, col. 4 (Civ. Ct. N.Y. Co.).
Moreover, contributions toward costs other than rent such as utilities and furniture may be included in calculation of "proportionate share" of rent. See 719 West 180th St. LLC v. Gonzalez, 11/6/2002 N.Y.L.J. 20, col. 3 (Civ. Ct. N.Y. Co.).
Charging a roommate rent in excess of his or her proportionate share of the rent is not a ground to evict. First Hudson Capital, LLC v. Seaborn, 54 A.D.3d 251, 862 N.Y.S.2d 501 (1st Dep't 2008), appeal withdrawn, 11 N.Y.3d 784, 866 N.Y.S.2d 610, 896 N.E.2d 96 (2008) and appeal dismissed, 11 N.Y.3d 894, 873 N.Y.S.2d 270, 901 N.E.2d 764 (2008).