Subject to the power of the Board of County Commissioners under § 21-105 of this title, the Washington Authority, in addition to the powers listed in this Division II and provided by local law, may: make mortgage loans; make rent subsidy payments to or for persons of eligible income; make construction loans and long-term mortgage loans to a person to produce housing for persons of eligible income; or waive maximum income limits for persons 65 years of age or older. The Washington Authority may sell its bonds at public or private sale in the manner and on the terms that it authorizes by resolution.