525. (1) Any expenses incurred by the [Municipal Commissioner] under any provision of this Act in respect of any material of fittings supplied or work executed or thing done to, upon or in connexion with some building or land which are recoverable from the owner or occupier of such building or land may, subject to the regulations, be declared to be improvement expenses if the [Municipal Commissioner] with the approval of the [Corporation], thinks fit so to declare them, and on such declaration being made, such expenses, together with interest thereon payable under sub-section (2), shall be a charge on the premises in respect of which, or for the benefit of which the expenses have been incurred.
(2) Improvement expenses shall be recoverable in installments of such amount not being less for any premises than twelve rupees per annum, and at such intervals as will suffice to discharge such expenses, together with interest thereon at such rate not exceeding six per cent per annum as the Executive Committee may fix from time to time, within such period not exceeding thirty years as the [Municipal Commissioner] with the approval of the [Corporation] may in each case determine.
(3) The said installments shall be payable by the occupier of the premises on which the expenses and interest thereon are so charged or, in the event of the said premises becoming un-occupied at any time before the expiration of the period fixed for the payment of such expenses or before the sum, with interest as aforesaid, are fully paid off, by the owner for the time being of the said premises, so long as the same continue to be unoccupied.