The purpose of a rehabilitation project is: to bring a building to a decent, safe, and sanitary condition in accordance with applicable codes and standards, including those for construction, health, safety, fire, and occupancy; to maintain the building in that condition; to make the building more useful and attractive; to conform the building to the appropriate minimum livability code; to provide, under applicable special loan programs: lead paint abatement; indoor plumbing; or shared, accessory, or sheltered housing; in the case of a loan or grant to an elderly household or a disabled homeowner, to modify or improve a dwelling to make it more accessible or functional for the occupants, if the building is, or after improvements will be, structurally sound and free of health and safety hazards; or to provide, under applicable special loan pilot programs, radon abatement or asbestos abatement. The applicable codes and standards under subsection (a)(1) of this section are: those in force in the political subdivision where the building is located; or those that the Department sets by regulation for that political subdivision solely for purposes of this subtitle, if the political subdivision lacks codes and standards that the Secretary considers sufficient to promote the objectives of this subtitle. With the approval of the local enforcement authority, the Secretary may allow exceptions to a code or standard to preserve the historic or architectural value of a building undergoing rehabilitation under this subtitle.