My friend sold his properties and rented, to prepare the fall in Housing Price. Is that a good idea?

Not sure does not sound like what people do

There wont be a fall due to scarcity

Your friend should buy stocks if interest in such strategy. Property in Singapore don't work this way.

My friend did the same thing more than 10 years back. By the way, she is still living with her in law as she is unwilling to buy back as prices have shot up too much.