In Illinois, when two parties enter into a real estate contract, the contract can be based on either consideration or collateral. A contract based on consideration is one in which each party agrees to do something in return for what the other party agrees to do. A contract on collateral base is one in which one party agrees to give the other party some type of security or guarantee that they will perform their obligations under the contract. Visit Now:www.collateralbase.com/real-estate/real-estate-contracts/