Private residence relief: dependent relative: rent free: financial help
In cases of this type, the claimant and the dependent relative will each acquire part interests in the dwelling house, as beneficial tenants in common, see CG70500+. Those part interests will be proportional to the respective financial contributions made towards the purchase price of the house.
For example, if the claimant has contributed £40,000 towards a dwelling house for a dependent relative costing £60,000, then they will have a 2/3rds interest in the house in respect of which they will be entitled to relief under TCGA92/S226 when the house is sold, assuming other conditions for the relief are met.
When considering relief on part interests which have been acquired in this way, you should not enquire into whether the dependent relative could have afforded the dwelling house without financial assistance from the claimant. The fact that the claimant has a part interest in the house as the result of their financial contribution to its purchase is sufficient to trigger the relief if the other conditions are fulfilled.