The Commission is authorized at Los Alamos to grant to occupants project-connected persons, and persons residing in the community both at the time of offering of an apartment house for sale and for the preceding six months, and to any of the foregoing persons acting together, such priority interests and priority rights for the purchase of the apartment house as the Commission determines to be fair and reasonable: Provided, That a first priority right to purchase may be granted only to an occupant or a group of occupants, or an assignee (whose membership or ownership is composed of occupants, or project-connected persons, or persons residing in the community both at the time of offering of an apartment house for sale and for the preceding six months, or any of the foregoing persons) of the priority interests of such occupants, who or which has obtained the priority interest of at least 60 per centum of the occupants of the apartment house: Provided further, That a second priority right to purchase may be granted only to an entity whose membership or ownership consists of occupants, or project-connected persons, or persons residing in the community both at the time of offering of an apartment house for sale and for the preceding six months, or any of the foregoing persons (provided that such entity has obtained the priority interest of at least one occupant), and whose membership or ownership equals in number, and occupies or agrees to occupy, at least 70 per centum of the housing units in the apartment house. The 15 per centum deduction specified by section 2325(a) of this title, the deduction provided by section 2326(d) of this title, the financing provisions of section 2362 of this title, and the indemnity provided by sections 2363 to 2366 of this title shall be applicable to such priority sales of apartment houses. Priority interests granted by the Commission under this section shall be transferable as the Commission may by rule or regulation prescribe, but no priority right to purchase shall be transferred except as provided by section 2333 of this title.