Keith Webber, 67, of Chard, Somerset, a will writer has been found guilty of fraud.
Mr Webber stole more than £280,000 from four elderly clients over nearly three years. His first victims were his own sister-in-law and her husband. The other victims were two elderly ladies living in London.
While they were still alive, Mr Webber persuaded or deceived his clients into paying him large sums of money and withdrawing cash from their bank accounts. Mr Webber continued to withdraw more money from their accounts after they had died.
He also prepared wills for his clients appointing himself as executor and his wife as the main beneficiary of their wills.
The court was told that Mr Webber conned one man into buying him an £11,000 Jaguar car, and into buying Mr Webber's wife a £3,000 funeral plan.
He is due to be sentenced on Friday and was told to expect a "considerable prison sentence".