Hi,
I have 2 types of CCTV in my house:
1. Fixed CCTV with hard disk - bought from Sim Lim square. 3 camera + a hard disk cost about $500+. Pro is that the hard disk can record up to 2 weeks worth of images. You don't need to keep taking memory card out and watch the past image anytime. Cons: Expensive, the camera cannot be rotated, need to lay wire to connect the camera to the hard disk.
2. Portable CCTV - Bought from Qoo10, brand is StarCam. No memory attached to the CCTV. Pro is that easy to install and able to rotate and cheap (less than $100 each). Con is unable to store memory, only real time pic.