Which one of this website is good and cheaper to buy stuff? Kijiji, ebay or amazon?

[Jake]

Don't forget the biggest classified ad site for the U.S. and North, Craigslist.org
If there's a section for your area, there's a chance of finding one that you can buy face to face and test before paying. Be sure you can identify the model, if you want to avoid stolen goods you could ask for an ID or get a licence plate, it's common to meet in a public place to reduce the chance of showing a thief your home, but that's a perfect setup for selling off hot goods as well.

http://geo.craigslist.org/iso/ca

out of town purchases are more dangerous, there are off shore posers and no seller track records like ebay.
Here's an example in Florida that popped up (No I'm not associated)
http://miami.craigslist.org/mdc/mob/3629964851.html