If A signs a contract with B so that A cancels B`s house for $500, A`s consideration is the service of painting B`s house, and B`s consideration is $500 paid to A. If A signs a contract with B so that A does not repaint his own house in a color other than white and B A pays $500 a year to maintain that agreement, there is also a consideration. Although A did not promise to do anything in the affirmative, A promised not to do something he was allowed to do, and so A was considered. The consideration of A for B is the tolerance of painting one`s own house in a color other than white, and the consideration of B for A is $500 per year. Conversely, if A signs a contract to buy a car from B for $0, B is still the car, but A does not give any attention, and so there is no valid contract. However, if B still gives ownership of the car to A, B cannot take back the car because, although it is not a valid contract, it is a valid gift. In general, consideration in the past is not a valid consideration and has no legal value. Previous considerations are considerations that have already flowed from promising to promising. That is, the act or tolerance of the promise is older than the promise of the promise.
The consideration in the past cannot therefore be used as a basis for claiming damages.  In general, a conditional consideration is a valid consideration. If there is no consideration in a contract, the contract becomes invalid and the courts may refuse to perform the contract. Sometimes a contract lacks consideration, although at first glance it seems that the parties are exchanging something of value. Second, what you are negotiating for does not have to meet the value standards of others, and the courts have always refused to comment on this issue. In other words, if you had offered to sell your bike to your neighbor and asked for his collection of antique cigar boxes in exchange, and your neighbor had agreed to pay that amount (i.e. give you his collection of cigar boxes for the bike), it doesn`t matter if the deal may seem unfair to some. You made an offer for the bike, your neighbour accepted it for review, and you both wanted to make that deal, and you are both allowed to do so; It is therefore a viable treaty. Whether someone else thinks it`s right or wrong is irrelevant until it`s unscrupulous. In addition to consideration elements, a contract must contain certain other elements to be enforceable. While these requirements vary from state to state, these requirements usually include: Consider the uncle`s situation above. If the same uncle had instead made the following offer to his 13-year-old nephew: “If you don`t smoke cigarettes, drink alcohol, swear or play cards for money before your 21st birthday, then I`ll pay you $5,000.” On the day of the nephew`s 21st birthday, he asks the uncle to pay, and this time, in the next trial, the nephew can win. Although the promise not to drink and play alcohol before the age of 21 was not a valid consideration (it was already prohibited by law), most states allow smoking at 18 and swearing, while some consider it vulgar, is not illegal at any age. Although smoking is prohibited by law until the age of 18, it is legal for people over the age of 18, and therefore the promise to renounce it completely has legal value. However, the uncle would still be exempt from liability if his nephew drank alcohol, even if this consideration is worthless because it has been combined with something of legal value; Therefore, compliance with the entire collective agreement is required. Systems based on Roman law (including Germany  and Scotland) do not need to be taken into consideration, and some commentators consider this unnecessary and have proposed abandoning the doctrine of consideration and replacing it as the basis of treaties.  However, legislation, not judicial development, has been presented as the only way to eliminate this deep-rooted common law doctrine. Lord Justice Denning said that “the doctrine of consideration is too entrenched to be overturned by a crosswind”.  For example, if A B offers $200 to buy B`s villa, luxury sports car, and private jet, there are still considerations on both sides. .