Paying interest

I am a 26 year old man with a job in the I.T field alhumduallah. I am currently living with my family and they are making lots of plans to buy a building with interest. They have already found a building and are planning to move in and live there. I don't want to be apart of interest and i never imagined being in this situation. As the youngest brother(i have 3 older brothers) my opinion doesn't hold much weight in the family. They think i dont know anything. They would like me to help with the payments in order to pay the building off as quickly as possible. Will i be sinfil for helping them make payments and what is your opinion about living in a house in riba? I can take care of myself as i am financially stable. And my teacher also said i can live at his madrasa for free and he recommended me to ask you. The biggest problem i see is that if i move out it may mess my relationship up with the family.