I want to sell my flat and buy a flat near my parents. Is now a good time to sell my property?

Hmmm maybe this article will help? Lots of grants and subsidies for resale flats near your parents. http://www.hdb.gov.sg/cs/infoweb/residential/buying-a-flat/resale/living-with-near-parents-or-married-child

If you have children, you might consider buying a home in a good school district.