The pre-contract of sale is a private document in which both parties agree to reserve the sale of a property, an amount of money is granted, fixed by the parties, in sign that in the future the purchase-sale contract will be signed. In general, the reservation is made for a defined period of time, during which the property can not be sold, so you will have enough time to take the necessary steps to request, for example, a mortgage loan.
When you get the property that adapts to all your needs it is advisable to make the reservation, otherwise a person may buy it or reserve it before you do.
