(a) The authority shall sell only those residential lots which have theretofore been leased by it, and such a sale shall be made only to the person who shall hold such lease, his assignee, or assigns. No conveyance of the fee simple title to any residential lot shall be made until the lessee of such lot has performed all the obligations regarding the improvement and erection of structures on the lot as are imposed by the lease.

(b) The authority shall sell no commercial property on which improvements were erected prior to March 1, 1957, but the authority may sell other commercial property in the same manner as provided by this part for the sale of residential lots. Alternatively, if such commercial property has not previously been leased, it may be sold directly by the authority, provided that the deeds for such direct sales must provide that unless all obligations contained in the conveyance as to improvements and erection of structures on such property are fulfilled, the property shall revert to the authority and the state, as their interest may appear.

(c) All sales of residential lots and commercial property, except for direct sales of commercial property provided in this Code section, shall be made at the conversion price set by the authority in accordance with Code Section 12-3-250, provided that any person who purchases any residential lot sold by the authority shall be entitled to credit on the purchase price to the extent of all payments made by him or his assignors or predecessors in interest on such lease, provided that such credit shall not exceed the purchase price of such lot. If such credit shall equal the purchase price for such lot, the lessee shall be entitled to a conveyance of the fee simple title to such lot, and the authority shall thereupon pay into the state treasury an amount equal to the value of the state's interest in such property as determined as provided in Code Section 12-3-249. The authority shall establish proper reserves to ensure that funds will be available for such purpose.

(d) No credit shall be allowed to purchasers of commercial property for any prior rental payments.