Section 6. The officer shall cause the land to be appraised by three disinterested persons, to be appointed, one by the creditor, one by the debtor whose land is taken or, if the debtor is absent from or does not reside in the commonwealth, by his agent or attorney if he has any known to the officer, and one by the officer. If the debtor is absent from or does not reside in the commonwealth and has no agent or attorney known to the officer or if he neglects within a reasonable time to appoint an appraiser, the officer shall appoint one for him.