Is a thing about the kind of trade you are doing, or even an on-line purchase - from a vendor or an individual - you send off your stuff or your money - then wait for their stuff or their goods to show up for you - is an element of trust there, that the other party actually did what they said that they would do, if you did your part. And, for an on-line individual trade, if the other party is legit - will be same concern about you. Go with your "gut" - you will sleep better. You are selling or trading a firearm; that other party is "acquiring" one - is multiple laws that kick in - some on you, some on that other party - is not quite like swapping for kitchen dishes.
Perhaps you will want to research the other party's past posts on social media - any past or other records of previous transactions - as he may or may not do about you - each forms an opinion about other, but is nothing "iron clad" guaranteed. I have had 100's of really great transactions - both on CGN and other internet sites - and got ripped off once - I sent an EMT and shortly after that, the user was "banned" and no goods ever showed up - was about when I thought that I was really comfortable with the idea. No doubt I would have "quit" with it, if that rip-off had been my first experience at it.
If you are totally new to this "game", or have been out of it for several years, you will discover Canada Post now has a host of "rules" related to sending a firearm by mail - might shock you to discover some of them - is not really like putting a hammer in the mail, and sending that off.
Nothing is "bullet proof" - we drove an hour to a nation wide vendor in nearby city - bought two patio furniture sets in big boxes - drove an hour home - part way through second box of assembling things, discovered that the second unit was packed in China with two right side arm rests and no left side one. So now what? Not really a ton of difference with a trade with an unknown-to-you individual? Vendor has our money - we did not get what we paid for. Following up now on "re-course" - but is PITA - even though no doubt will eventually be worked out - in months, though, maybe ...
And, for some "face-to-face" CGN transactions, I or the other party (or both of us!!) had driven 3 or 4 hours to get to our "meeting" place, to "do" the transaction - sometimes items could not be mailed - ammo, powder, primers - sometimes one or other of us wanted to actually see the thing before payment occurred. Do not have to use mail - from your OP, you are nearly in the same province as the other party - not like you have to drive to the Maritimes from Saskatchewan for that deal - but is always up to you - nobody is forcing you to do anything, ever.