If you hand this to lawyers the buyer will no doubt be advised of risks. Potential risk of not getting possessory title after purchase.
Can you not obtain possessory title first?
Legally, you cannot sell something you do not own. You do not have title or any interest in the land as yet.
Potentially the contract could be void, if you sold the land and the buyer's possessory title application failed.
You can proceed but I could not give any guarantee that it is valid and that you would not be exposed to any action from the buyer in the future. If it does not work out the buyer would have 6 years to claim against you.