Hey, Welcome to the forums. Glad you have decided to come to the light! lol
As RITZ has said, getting an M4, or any airsoft weapon is as easy as getting age verified with us. There is an unimaginable amount of rifles for sale used and new on/through this site. ESPECIALLY M4s :P
Please take some time to read all
of the FAQs in the FAQ section, there is VERY
important information there for you, including information on how to get Age Verified.
Also included in the FAQs is information about what NOT to buy from outside Canada - I suggest this be one of your first reads.
One thing you will find on ASC is that we are not here to spoonfeed you. Please show some initiative and research topics on your own, pretty much any question you can think of has been asked before, so please use the search function up top
Have fun, and welcome to the sport