I. THE CONTRACT OF SALE, This contract is (i) consensual, (ii) real, (iii) bilateral (iv) onerous. For representation of money, we understand usually a cheque, a promissory note or a bill of Exchange. Despite the consensual nature of the contract, the sales contract causes real effects (transfer of property). Consequently, as a result of the preceding provisions, we could distinguish two phases in a sales contract: (1º) obligational and (2º) real. Obligation Phase: the contract is PERFECTED when the mutual consent on the sale conditions (price, object, term, quality…) is given by both parties. From that moment on, both parties stay reciprocally obliged: the seller to deliver, and the buyer to pay the price. 2) Real phase: the contract is COMPLETED when, in fulfilment of its duties, the seller transfers the property of the thing to the buyer, by means of the TRADITIO (Delivery), and the buyer pays the price to the seller. II. THE CONTRACT OF LEASE OF URBAN PROPERTIES; This contract is ruled by Act 29/1994 on Urban Leases (Ley 29/1994 de Arrendamientos Urbanos), which distinguishes between (i) leases for dwelling and (ii) leases for a purpose other than dwelling. (A) URBAN LEASES FOR A DWELLING; The lease of a real property for a dwelling is regulated by Title II of Act 29/1994, whose provisions are mandatory and cannot be modified in prejudice of the tenant, under sanction of nullity. (B) URBAN LEASES FOR PURPOSES OTHER THAN A DWELLING, The dwelling may also be rented for seasonal, industrial, commercial, or any other lawful activity other than dwelling. IV. CONTRACT OF LOAN:(A) SIMPLE LOAN (LENDER – BORROWER), One of the parties delivers to the other money or another fungible object, under the condition to return the same amount of the object, and of the same kind and quality. This contract may be remunerated (interest) or not. The party who receives as a loan in money or another fungible object, acquires the ownership thereof, and is obliged to return to the creditor the same amount thereof, of the same kind and quality. If the object loaned is another fungible object, or an amount of un-minted metal, the debtor shall owe an amount equal to the amount received, of the same kind and quality, even if there has been an alteration in its price. Despite no interest shall be due unless explicitly covenanted, the borrower who has paid interest without this being stipulated cannot claim the refund. (B) COMMODATUM (COMMODANS – COMMODATARIUS), One of the parties delivers to the other a non-fungible object so that the other may use it for a certain time and return it. This contract is essentially gratuitous. The “commodans” shall retain ownership of the object loaned and its fruits. The “commodatarius” shall acquire the just use thereof. (a) Obligations of Commodatarius 1. The “commodatarius” shall be obliged to pay the ordinary expenses required for the use and conservation of the object loaned. 2. The “commodatarius” shall not be liable for any impairments to the object as a result of ordinary wear and tear and without negligence on his part. 3. The “commodatarius” may not retain the object loaned with the pretext that the “commodans” owes him an amount. (b) Obligations of Commodans: The “commodans” may not claim the object loaned until after it has completely served the use for which it was loaned. Notwithstanding the foregoing, if, prior to such expiration, the “commodans” were to have urgent need for the object, he may claim its return. If no duration of the commodatum or use have been covenanted the “commodans” may claim it at will. The “ commodans” shall pay any extraordinary expenses arisen during the term of the contract for the conservation of the object loaned, provided that the “commodatarius” gives notice before making them, unless if they were to be so urgent that one cannot wait for the results of the notice without danger. A “commodans” who, being aware of the defects of the object loaned, did not advise to the “commodatarius” shall be liable to the this for any damages suffered.