Agreement of sale

One of a customer showed his interest to purchase my house. I want to make agreement of sale on 100 rs bond paper. Clauses : 1. 60 % payment in 10 days and remaining 40 % at time of registeration in 3 months 2. If I fail to sell my property I will pay money back plus 20 % extra on money he paid advance to me 3. If he fails and want to cancel agreement then i will return 50 % what he paid to me. As I am going to purchase a new flat with money he pays me in advance and I don't have other source of money . In case if he cancels the deal . I need to pay only 50 % back to him correct as per clause we mentioned? Also what is better to make a sale agreement on bond paper of 100 with notary it or to get the sale agreement registered ? In case any issues happen will I be able to go to court for it ? I want to be on safe side as i don't want deal to get cancelled as my only source of money is what I get by selling my house and cant pay it back once I purchase new house using money the buyer pays me. By making agreement of sale in any way can the buyer show his right on my property?