what are my rights

[pb5555]

my landlord has lied to me twice once over a aparment i was surpose to get and he let some else move in and a house he made me move cause someone else wanted to buy it, i'am disable and can't keep moveing all the time, he put me in another house and i ask him to write on paper the rent i pay every month and that he would'nt sell it as long as i lived here unless it was to me to my surpise he did and he also signed his name i also had a friend that was present at the time and she signed it too in front of him ,now with out notice his wife a realator shows up to show the house ,i was never told they was going to sell the house or even ask it i wanted to buy it ,i have lived here for 1 and 1/2 years always have paid my rent and never been late once,i need to know my rights is that paper he signed worth anything and can i stop them from selling the house ,what are my legal rights , i need some advice thank you