I have seen videos of foreign adults and kids playing with home made rocket models or they can buy easily online. Some of the rockets can shoot upto few hundred foots high.
Are we allowed to made a rocket model by ourself in Singapore?
The below url shown some videos collection of adults and kids that make their own rocket models. Have some information on how to DIY rocket models also.
NASA links in the page also provide free softwares for rocket models and environment calculation.
http://futtech.blogspot.com/2007/07/home-made-rocket-motor.html