When you make an Off-Plan purchase, you are essentially buying a home that does not yet exist. There are quite a few details which need to be verified before you decide to go ahead.
I once saw a plan for a beachfront development in Muizenberg. I liked what I saw on paper and transferred a reservation fee to the attorney. It then transpired that the developer had sold me an apartment on the eighth floor. Imagine my surprise when I discovered that they only had permission to build six floors! I insisted that the attorneys refund me and they did.
On another occasion, I considered signing up for a sea side apartment on the West Coast. It turned out however that the land in question was actually the ocean floor. The Developer had assumed that because he was building off the ground, and at the height of a third floor, everything would be ok. The Development company was eventually declared insolvent.
If you are considering the option of making an Off-Plan purchase, researching the Developer and Estate Agents involved would be a good starting point. You should also check out some of their completed projects.