Subject to the provisions of section 4b-30, the Commissioner of Administrative Services may enter into contracts for the construction upon state-owned land of buildings or facilities or both, and for the subsequent leasing of such building or facilities to the state to meet the needs of agencies and institutions, without first leasing the underlying state-owned land to the developer. Such contracts shall contain provisions providing for the state to buy the buildings and facilities for a lump sum at stated times during or at the end of the lease term or, at the state’s option, to buy the same by paying the purchase price in installments.