A homeowner is experiencing significant issues with a building redevelopment project that began four years ago. The builder initially agreed to an extra 70 sqft for a token payment, half of which was in cash. Now, the builder is demanding an additional £5,000 in cash, which the homeowner cannot afford and has refused to pay in cash, preferring bank transfer. The builder has since stopped paying rent and is unresponsive. The homeowner is seeking advice on how to proceed, including dealing with the builder's refusal to pay rent, cancelling the additional area purchase, recovering the initial cash payment, and the stress this is causing their elderly parents.