When I got my RPi2, I had an old EasyCap (empia2861 chipset) so I tried to see if I could get a picture using a cheap (i.e. eBay) TVL 640x480 working (RPi2->EasyCap->TVL). Well, I can say it "works" because there is a picture, but the quality looks like an old CRT TV scan and it exhibits screen tears every so often. It's not horrible - would be good enough just for seeing who is at the door - but nothing great. (Raspbian recognizes the empia chip right away, and using mplayer displays the camera image).
I did recently get a Pi Zero, and just for kicks decided to see if I could transfer the functionality over to it (and use the RPi2 for something else). Yup - works and image looks just the same. Only need a small, unpowered USB hub to plug the EasyCap into - but I had to make my own USB-male to power-barrel-connector to feed the CCTV camera juice. It runs fine with power from the Pi Zero (thru the 4 port hub) without any external/extra power required.
The setup is wifi dongle, EasyCap, and USB-male to barrel connector all in the hub, which is connected to the PiZero with an OTG.
I have VNC autostart so I can get at it remotely.