No crypt, room, or space in the structure shall be sold or offered for sale before the structure is entirely completed, unless and until the agency selling the crypt or niches, enters into an agreement whereby it agrees to refund to each and every purchaser all sums of money paid by each, together with legal interest on all sums of money, in the event it fails to complete the structure within the time which shall have been limited by the city or town wherein the structure is located, which agreement shall be entered into with some bank or trust company or other organization as trustee for the persons as directed by the city or town, nor until the agency shall also have made, executed and delivered to the trustee, its bond, with adequate security, if required, conditioned upon paying to the trustee a sum of money sufficient to provide for the refund previously provided and to provide for the repair, maintenance, and replacement of the structure, or shall have paid or delivered to the trustee a sum of money or other property sufficient for these purposes, the amount of the bond, payment, or delivery of property and the security on the bonds, if any shall be required, to be fixed and determined by the city or town wherein the structure is located.