Short answer: Clause allowing cancellation if not completed by deadline. Protects from delays. Ensure it works both ways.
A sunset clause lets you or the developer cancel the contract if the building is not finished by a certain date. It protects you from endless delays. But some developers use it to cancel if prices rise, then resell for more. Make sure the clause works both ways and has a firm deadline.
Deadline: 18 months from contract date
If Missed: Buyer can cancel and get deposit back
Developer Abuse: Developer cancels when prices rise 20%
Protection: Ensure clause requires developer compensation if they cancel