I blame my real estate agent who told me the house was at a good price.
Malpractice is a type of negligence.
You can sue someone for negligence if that person had some duty to you or a general duty to everyone to act in a certain way, they failed to act in that way, and that failure caused injury to you. The example everyone knows is that every driver has the duty to use reasonable care in operating his car, including obeying traffic laws. If he fails to stop at a traffic light and smacks into you, you have a good case for negligence. Malpractice is the same except that the professional you are suing must hold himself out as having special skill, training or experience in a particular field. Medicine, law and architecture are typical professions of that type.