Section 24. Such petition shall set forth a description of the estate to be mortgaged, the amount of money necessary to be raised and the purposes for which such money is required, and, if made to a probate court, shall be made in the county where trustees were appointed, if the trust was created by will, or, if it was not so created, in the county where the estate, or a part thereof, which is the subject of the petition is situated. The decree of the court upon such petition shall fix the amount for which the mortgage may be given and the rate of interest which may be paid thereon, and may order the interest and the whole or any part of the money secured by the mortgage to be paid from time to time from the income of the property mortgaged.