Section 50. If the town becomes the purchaser, the deed to it, in addition to the statements required by section forty-five, shall set forth the fact that no sufficient bid was made at the sale or that the purchaser failed to pay the amount bid, as the case may be, and shall confer upon such town the rights and duties of an individual purchaser. Every such deed and every instrument of taking described in section fifty-four shall be in the custody of the town treasurer, and there shall be set up on the books of the town, whether kept by the treasurer or otherwise, a separate account of each parcel of land covered by any such deed or instrument, to which shall be charged the amount stated in the deed or instrument, the cost of recording the same, and, upon certification in accordance with section sixty-one, all uncollected taxes assessed to such parcel for any year subsequent to that for the taxes for which such parcel was purchased or taken, with all legal costs and charges thereon, including interest accrued up to the date of such certification, until redemption, foreclosure or assignment. The tax title account hereby required to be kept, or a duly authenticated copy thereof, shall be prima facie evidence of all facts essential to the determination of the amount necessary for redemption. The town treasurer shall institute proceedings for foreclosure as soon as such proceedings are authorized by sections sixty-two and sixty-five. The commissioner may at his discretion institute proceedings in the name of the treasurer in the event that such proceedings are not instituted by the treasurer. Any expense incurred by the commissioner hereunder shall be assessed against the city or town and collected in the same manner as expenses for auditing municipal accounts under the provisions of section forty-one of chapter forty-four.