home security camera configuration

[michaelbr 0]

I'm new to this, and thinking in installing a video surveillance for home, I'm new to this subject, so please bear with me, here are my questions:

1) when buying a video monitoring kit, they ask which size of memory required, how do I calculate the memory size based on the resolution of the camera? 

2) do I need to add an external HD for storage?

3) is there a site/video showing specs of the system for beginner based on your needs?

Thanks for your comment/suggestion