In this article the author presents the construction and functions of a contract of sale of future goods, in particular pertaining to real property under construction. The sale of future goods contract guarantees the buyer that he will obtain the property right of the sold good automatically upon its existence (or sometimes at a later stage), the seller, that he will sell this good to the buyer. Consequently, the buyer may gain from the fact that the seller will not sell such goods to a third party and the seller may gain the price paid upon the signature of the contract, which will enable him to finance the construction of the future good. Such benefits of the sale of future goods contract can also be used in order to sell real property that is under construction. The guarantee and financing function of the sale of future goods contract is especially important in real property development projects. Polish regulations incorporated in the Civil code enable parties to conclude sale of future goods contracts. Upon the signature of such a contract, the buyer obtains the right to acquire the ownership right of the future good. The ownership right is transferred onto him at the time when the buyer obtains the possession the now existing future good. Regulations pertaining to sale of real property differ substantially in most European countries. The analysis in this article indicates that the sale of real property under construction has been regulated in some countries and that constructions such as VEFA (France) have had a positive impact on these legal systems.