A judge heard that former mobile phone company employee William Edgar pestered his mother Mary to put her Greenock home in their joint names. He promised her a new kitchen and new carpets for the Nicolson Street flat but instead blew most of the loan they obtained on it within days.
Mrs Edgar - who was 74 when she signed over a half share in the flat for "love, favour and affection" - asked the Court of Session in Edinburgh to scrap the deal.
Judge Lord Burns agreed that the arrangement made in December 2008 should be over-turned after hearing about Mrs Edgar's medical problems.
In his written ruling issued yesterday, Lord Burns also said: "I must record that I did not form a good impression of the defender (William Edgar) when he gave his evidence. I did not find him credible or reliable."
After he became a joint owner of the flat a mortgage loan of £25,273.95 was credited to Mr Edgar's account on December 15 2008.
Four days later Mr Edgar paid off debts of £3778 and £9953 and bought a car for almost £5000.
Lord Burns rejected Mr Edgar's claim that his mother knew perfectly well what she was doing.