(a) The property shall be suitable and principally designed for the intended use, as provided by the applicable section of the Act under which the mortgage is insured, and have long-term marketability. Design, construction, substantial rehabilitation and repairs shall be in accordance with standards established by the Commissioner.

(b) A project may include such commercial and community facilities as the Commissioner deems acceptable.

(c) The improvements shall constitute a single project. Not less than five rental dwelling units or personal care units, 20 medical care beds, or 50 manufactured home pads, shall be on one site, except that such limitations do not apply to group practice facilities.