There are disputes over a buyer`s powers with respect to violations of this requirement.     Essentially, a contract is an agreement that, by law, recognizes that enforceable obligations are necessary.  The calculation of the arbitral award in applicable South African law is different from that of Roman law, in which the amount awarded would be calculated on the basis of the difference between the price actually indicated and the price the buyer would have paid had he been aware of the default. In other words, it is a subjective test. In South African law, the degree of relief is usually the difference between the actual purchase price and the value of the item in its defective condition.  The value of the defective thing must be determined as is the case for the non-delivery of the thing sold: on the basis of the market price, if there is one. If no market price is established, the best available evidence must be used to determine the true value of the sale. Another way to assess the amount that can be repaid is to refer to the costs associated with eliminating the shortage that existed at the time of the sale and/or to remedy any deterioration that could have resulted from the default. Repair costs can only be considered in reasonable circumstances.  The seller is required to provide the thing sold without defects or illnesses. Unlike coercion and undue influence in cases of illegitimate pressure or alleged unlawful influence, which depends on an abuse of trust, other cases of a vulnerable person avoid an agreement simply because they are vulnerable and exploited. In the Medina, the Court of Appeal found that a group of pilgrims who had sunk on a Red Sea rock did not have to pay $4,000 promised to a rescue ship because the „saviors“ had taken advantage of the vulnerable situation of the pilgrims.
To avoid unfair enrichment, the Court replaced an arbitration award of $1800. Similarly, in Cresswell, Ms. Cresswell gave her ex-husband her share of her common assets in exchange for the release of mortgage repayments, which then earned her a profit of $1400. As Potter took advantage of Ms. Creswell`s ignorance of real estate transactions, Megarry J felt that the agreement was void.  One possible exception to this model, which is now very limited, is the „no is factum“ defence, which originally applied in the 19th century in favour of illiterates who allowed a person to invalidate a signed contract if it was fundamentally different from what he intended to do.  In Lloyds Bank Ltd/Bundy, Lord Denning MR suggested that it was time to place all cases in a single doctrine of „unequal bargaining power“.  This would have allowed an agreement to be avoided if, in the absence of independent advice, a person`s ability to negotiate on better terms had been seriously compromised and had essentially given the courts more leeway to amend contracts for the benefit of weaker parties. The idea of a uniform general doctrine was rejected by some members of the House of Lords from 1979.  However, specific legislation such as the Consumer Credit Act 1974, the Landlord and Tenant Act of 1985 or the Employment Rights Act of 1996 create specific rights for contracting parties that lack bargaining power, as well as specific legislation that rewrites a disclosure obligation and good faith. Just as there is no uniform theory of bargaining power, a uniform doctrine of contractual freedom was dismantled long ago, where the parties do not do business in the course of business.
 For most ordinary and day-to-day business transactions, the conclusion of a sale contract and the surrender of the property is done by delivery of the res immediately.