The performance may consist of an act other than a promise, or a forbearance, or the creation, modification, or destruction of a legal relation.
The landlord and tenant come together to discuss the terms of the exchange (most of the time, the leasing is outlined in a contract).
Also, modifications to existing lease agreements (as opposed to the creation of a new lease agreement) do not require consideration,[2] nor do modifications to existing sale contracts.
The first is "benefit-detriment theory," in which a contract must be either to the benefit of the promisor or to the detriment of the promisee to constitute consideration (though detriment to the promisee is the essential and invariable test of the existence of a consideration rather than whether it can be constituted by benefit to the promisor[4]).
The main purpose of the shift from benefit-detriment to bargain theory is to avoid inquiries into whether consideration is adequate.
However, in other[clarification needed] jurisdictions, the court will reject "consideration" that had not been truly bargained for.
The traditional notion that courts won't look into the adequacy of consideration, an ancient notion in the English common law, doesn't square with the benefit-detriment theory (in which courts are implicitly analyzing if the parties are receiving a sufficient benefit) but does square with the bargain theory (in which only the subjective intentions of the parties are considered).
The second is the evidentiary requirement - parties are more likely to commemorate, or at least remember, a promise made due to a bargaining process.
The third is the channeling requirement - parties are more likely to coherently stipulate their specific desires when they are forced to bargain for them.