To start off, the components selected are older than today's standard (the AMD FX line is from 2013), and you should get better performance for the same money.
Besides watching videos from channels such as LinusTechTips, you could google the parts yourself, looking at their release dates on for instance Wikipedia.
Assuming that site sells or trades used parts, and AMD FX cpus are notorious for running hot (especially if older), I'd say you're better off spending that $500 CAD on new parts.
The only things worth your money may be the two monitors.
While it may be a decent deal, I personally dislike buying used goods. I don't know the quality of the parts I'm buying, it comes with no insurance. You won't know how long those parts will last, whether there's something wrong with them or not, and if you save up a little more, or opt for less, you could get new parts that aren't going to cause you a headache.
If this is going to be a fun and whatever setup, you could take the risk and purchase it. For your main setup and daily use computer, I'd strongly suggest buying new parts.
https://ca.pcpartpicker.com/list/fHRrkT
*BIOS update can be acquired and put on a USB drive to flash the stock bios.
I've made a suggested parts list. It can be cheaper if you ditch the monitor, but I don't know whether you have a 1080p monitor yet, so I put it in there to be safe.