This subtitle does not apply to: the sale or rental of a single–family dwelling, if the dwelling is sold or rented without: the use of the sales or rental facilities or services of any: real estate broker, agent, or salesperson; agent of any real estate broker, agent, or salesperson; person in the business of selling or renting dwellings; or agent of a person in the business of selling or renting dwellings; or the publication, posting, or mailing, after notice, of any advertisement or written notice in violation of this subtitle; and with respect to discrimination on the basis of sex, sexual orientation, gender identity, marital status, military status, or source of income if the source of income is low–income housing assistance certificates or vouchers issued under the United States Housing Act of 1937: the rental of rooms in any dwelling, if the owner maintains the dwelling as the owner’s principal residence; or the rental of any apartment in a dwelling that contains not more than five rental units, if the owner maintains the dwelling as the owner’s principal residence. The use of attorneys, escrow agents, abstractors, title companies, and other similar professional assistance as necessary to perfect or transfer the title to a single–family dwelling does not subject a person to this subtitle if the person otherwise would be exempted under subsection (a) of this section. In this subsection, “housing for older persons” means housing: provided under any State or federal program that is specifically designed and operated to assist elderly persons, as defined in the State or federal program; intended for, and solely occupied by, persons who are at least 62 years old; intended and operated for occupancy by at least one person who is at least 55 years old in each unit; or that meets the requirements set forth in regulations adopted by the Secretary of Housing and Urban Development under 42 U.S.C. § 3607(b)(2)(C). “Housing for older persons” includes: unoccupied units, if the units are reserved for occupancy by persons who meet the age requirements of subparagraph (i) of this paragraph; or units occupied as of September 13, 1988 by persons who do not meet the age requirements of subparagraph (i) of this paragraph, if the new occupant of the unit meets the age requirement. The provisions in this subtitle concerning familial status do not apply to housing for older persons. The prohibitions in this subtitle against discrimination based on source of income do not: prohibit a person from determining the ability of a potential buyer or renter to pay a purchase price or pay rent by verifying in a commercially reasonable and nondiscriminatory manner the source and amount of income or creditworthiness of the potential buyer or renter; prevent a person from refusing to consider income derived from any criminal activity; or prohibit a person from determining, in accordance with applicable federal and State laws, the ability of a potential buyer to repay a mortgage loan.