What is the test for undue influence in real estate transactions?

In Geffen v. Goodman Estate, 1991 CanLII 69 (SCC), [1991] 2 S.C.R. 353, Wilson J. wrote (at p. 378): What then must a plaintiff establish in order to trigger a presumption of undue influence? In my view, the inquiry should begin with an examination of the relationship between the parties. The first question to be addressed in all cases is whether the potential for domination inheres in the nature of the relationship itself. This test embraces those relationships which equity has already recognized as giving rise to the presumption, such as solicitor and client, parent and child, and guardian and ward, as well as other relationships of dependency which defy easy categorization. Having established the requisite type of relationship to support the presumption, the next phase of the inquiry involves an examination of the nature of the transaction. When dealing with commercial transactions, I believe that the plaintiff should be obliged to show, in addition to the required relationship between the parties, that the contract worked unfairness either in the sense that he or she was unduly disadvantaged by it or that the defendant was unduly benefited by it. From the court’s point of view this added requirement is justified when dealing with commercial transactions because, as already mentioned, a court of equity, even while tempering the harshness of the common law, must accord some degree of deference to the principle of freedom of contract and the inviolability of bargains. Moreover, it can be assumed in the vast majority of commercial transactions that parties act in pursuance of their own self-interest. The mere fact, therefore, that the plaintiff seems to be giving more than he is getting is insufficient to trigger the presumption. By way of contrast, in situations where consideration is not an issue, e.g., gifts and bequests, it seems to me quite inappropriate to put a plaintiff to the proof of undue disadvantage or benefit in the result. In these situations the concern of the court is that such acts of beneficence not be tainted. It is enough, therefore, to establish the presence of a dominant relationship. [emphasis added]