If it be clearly shown, independently of any admissions in the answers, that the interest of the infant, insane person, convict or beneficiaries in the trust, as the case may be, will be promoted, and the court be of the opinion that the rights of no person will be violated thereby, it may decree that such estate or any part thereof be sold, leased, mortgaged or encumbered by a trust deed, on such conditions and upon such terms as to the court shall seem to the best interests of such infant, insane person, convict or beneficiary in a trust, as the case may be, and in case the sale of such land is decreed, the purchaser, when the sale is on credit, shall be required to give ample security, and, if the sale be of real estate, a lien shall be retained thereon to secure the payment of the purchase money.