I bought a house on contract

(Repost i removed all violations) So I bought a house on contract from my grandmas neighbor and basically how it works is that i pay x amount of money each month for my mortgage in a check written out to the guy who sold me the house which he then puts into his bank until the house is paid off but What happens if I give him the money and he just decides one day to not pay it, do I just lose my house?