According to the main principle of civil law, the parties are free to define their legal relationship as they see fit, while the legislator imposes only some minimum requirements that should be observed. In case of the sale agreement, it is the requirement to agree on the price. The price can be specified as a certain amount or by indicating the basis for its determination. On the other hand, the practice of economic transactions in investment properties shows that the market value of such a property depends on numerous factors beyond the control of the parties to the transaction. This article analyses the practice of notaries, case law, and views of legal scholars concerning preliminary agreements and sale agreements in the context of the calls for greater security and speed of investment property market transactions.