Being a .ca doesn't matter. As google notices inbound links start disappearing(as one would suspect as webmasters notice the original website is no longer there) they will either discount or remove the
pr all together. The quicker you get content on there the better. In the best case scenario you may be able to maintain the
pr as it is. I've grabbed
pr 4 and 5 .ca's before and have been able to maintain the
pr in the past.
You can sell text links... but google has cracked down on the practice. Sites buying links can be penalized if caught, and the same goes for the website selling the links - penalty being a drop in
pr. If you don't care about losing the
pr, and the buyer doesn't care about the possible risk, you can make a quick handsome return selling pr8 links.