Question: What is $($potentially$)$ wrong with this contract?

Q: Ray is and old man who is very sick and in hospital. Ray's illness leaves him feeling very tired, and often incoherent. Barbara, a local property expert, has been eyeing off his home for some time. Barbara visits Ray in hospital, along with her lawyer, to convince him to sell her his house for a price much lower than the current market value. Ray has no knowledge of the current market, nor does he have the capacity to read or understand legal documents.