New York Consolidated Laws, Civil Practice Law and Rules - CVP § 601. Joinder of claims

(a) The plaintiff in a complaint or the defendant in an answer setting forth a counterclaim or cross-claim may join as many claims as he may have against an adverse party.  There may be like joinder of claims when there are multiple parties.

(b) Two or more plaintiffs may join no more than five claims in any one action or proceeding against the same defendant arising out of separate consumer credit transactions, provided that the plaintiffs are represented by the same attorney.