Section 50A. In the event of the filing of a certificate under clause (38) of section five of chapter forty in respect to any particular real estate held by a town under a purchase or taking for non-payment of taxes, the collector shall make a written demand upon the owner of record thereof requiring that he take certain specified action to preserve, care for or maintain the same or protect by insurance or otherwise the town’s interest therein, within a period fixed in the demand the expiration of which, except in case of emergency, shall be not earlier than seventy-two hours after the date on which the service of said demand is completed. Said demand shall be served upon such owner of record by mailing the same to him at his last known residence or place of business, postage prepaid, and by posting a copy thereof upon such real estate. In default of action in compliance with such demand, the town may proceed to take the specified action and the expenses incurred on account thereof shall be included in the tax title account for such real estate and be treated in all respects as part of the legal costs and charges of collection.