Welcome first off.
Lets see start off by adding more info to your profile especially your age. Next start reading the FAQ section, much of the information you seek is there. As for Canadian retailers the pull down menu has some but, only 007 and A&A sell airsoft. Also find out who is your age verifier where you live and arrange to pay him/her a visit. Once your age verified, you will be able to browse the classfied sections for used equipment etc.