You did not give any details about the sinking, like is is all around or on one particular wall? Is the drainage bad? Do you have ponding around the foundation? Is it the foundation, or more specifically joists sagging?
Come back with more specs and I am sure that someone could give you some good advice, but I am sure that no one will say build a new home.
All homes settle more than others and this is remedied everyday in the country. I just had mine fixed and it hurt some, but not as bad as re building.