A Conditional Contract
This contract is only binding once all the conditions have been satisfied. Once all the conditions have been met the contract unconditional.
Even then the contract may only be voided if a condition is not met ' one party cannot simply change their mind.
If a condition has been included for the benefit of one party they can waive their rights under the condition and the contract continues as if that condition was never included eg A valuation or building inspection.
HAVE YOUR LAWYER CHECK THE CONTRACT AND DISCUSS IT WITH THEM BEFORE YOU SIGN THE CONTRACT OR WANT TO MAKE ANY CHANGES TO AGREED CONDITIONS.