Courtyard lease ?

Hi !

I am a newbie looking for a small investment property .
I am currently looking at a single level unit which has a private courtyard. The property is fenced off with the private courtyard. However, the private courtyard is not part of the title but under a 99 years lease (under the body corporate). Is this common ? If so, what do I have to look out for ? The real estate agent told me that I can make any changes to the countyard as I am pleased, as if it is my own land. Is this correct ? I am a bit doubtful as it is not part of the title.
Your advice would be greatly appreciated.

Thanks,
Mark. [blink]