Until the signing of the title deeds at notary between buyers and vendors and the balance has been paid to the vendors, we are never 100% percent certain a completion on the sale of the property will take place, even if the due diligence and legal searches on the property have been completed.
After saying this, once all the legal searches have taken place, the special conditions of the sale have been accepted by all parties involved and the private purchase contract has been signed and 10% of the purchase price has been paid by the vendor, we can be 98% certain that the sale will take place.
Pro Tip:  By organizing the buying and selling process in three stages: Deposit, signing of Private Purchase Contract and Completion, both vendors and buyers increase the opportunity of a successful sale to 99,99%. If vendors do not take a deposit or decide to go from deposit to directly signing title deeds, jumping the singing of the Private Purchase Contract, there is a strong possibility of misunderstandings between both parties during the process, ultimately leading to the sale of the property falling through.