My son is living in a house which he owns and his girlfriend is paying him rent. He also has some capital in shares. I have been told that, if they were to split up after living together for two years she would have a claim on his money. Is this correct?
No. The two-year rule applies only on the death of one of the partners. Your son’s girlfriend is unlikely to have any claim on his house or capital if they separate unless she makes a substantial investment in the property or your son promises (either verbally or in writing) that she will have a share in it. If they marry or have children the position will change.