N.Y. Comp. Codes R. & Regs. tit. 20 § 132.13
A business, trade, profession or occupation (as distinguished from personal services as an employee) is carried on by a nonresident wholly within New York State when the activities described in section 132.4(a) of this Part are carried on solely within New York State, and no such activities are carried on outside New York State, even though the nonresident or such nonresident's representative travels outside New York State for purposes of buying, selling, financing or performing any duties in connection with the business, and even though sales may be made to, or services performed for, or on behalf of, persons or corporations located outside New York State. If a nonresident individual carries on a business, trade, profession or occupation wholly within New York State, all of such nonresident individual's items of income, gain, loss and deduction attributable to the business are derived from or connected with New York State sources. With respect to a nonresident's income from, and deductions connected with, the rental of real property, and gain and loss from the sale, exchange or other disposition of real property, see section 132.16 of this Part.
N.Y. Comp. Codes R. & Regs. Tit. 20 § 132.13