Hi, suggest to go for registered mortgage deed for both agricultural land and guest house. Also take a special irrevocable power of attorney (registered) after registration of mortgage. So typically you should have the following.
a) loan agreement duly stamped.
b) promissory note.
if documentation is proper you can recover your money within 1 year.
c) registered mortgage deed and
d) special power of attorney.
Also ensure that loan is disbursed through cheque and post dated Interest cheques for entire duration of loan and principal amount cheque. Get three to four reliable witnesses.if documentation is proper you will recover your money within 1 year in case of default by borrower.