They are not living in the house. They bought it as a rental property, and are letting my sister stay there while they fix it up. I am not currently living with them, but probably would while I build this addition. Money is something we still have to finalize, but they will make it worth my while.
About how much can one expect to spend on materials for a modest one bedroom addition? I realize that this is a near impossible question to answer without knowing the details, but some ballpark figures would be much appreciated.