If the loan is genuine, then make sure that you have the source to show your income to fund such debt.
If source is there, then make sure that the rs.20/- stamp paper is printed by using the words for example " I A , aged 34 years son of B, identified by aadhar 12343434 residing at C along with my family (wife and 2 sons). I am occupied as ,,,,,,. I incurred an expense of 3L which i am unable to fund due to insufficient funds in my savings bank a/c vide 12343444 in bankl abcd at branch. In order to meet the expense of 3L, i am constrained to borrow from Mr.X Rs.3lakhs (Three lakhs only) with a simple interest at the rate of 16% per annum. I bind myself to repay the principal amount of 3L along with the interest of 16% per annum on 5th of every month. I also bind my wife Mrs. xxxxxx D/o identified through aadhar number.... through this loan agreement who is the legal representative to represent on my behalf in the case of non-repayment of the outstanding loan amount as on the date it falls due. In furtherance of this loan agreement dated 18-jan-2018, I also undertake to duly repay the principal loan amount along with the interest within 12 months from the date of acceptance of the loan amount. i issue 12 post dated cheques duly signed by me for the principal amount of Rs.3L and interest calculated at the rate of 16% per annum. Also, in furtherance off the loan agreement, my wife consented voluntarily to stand as surety and affixing her signature for having stood as surety.
This loan agreement has been duly signed and executed before the witness whereof my signature, surety's signature and witnesses signature, identity (aadhar) are affixed.
This is just a draft.
Get the cheques of the bank's branch which is specified in the agreement.
Ensure to get a copy of his previous signature in some other records and compare with the current one to ensure reliability. Similarly, his wife signature as well.