My two lengthy university assignments both started with an L visa. First time i was with an NGO who handled it all. Second time, the Z visa was sent to me.........by regular mail by a dunce in the FAO, and hadn't arrived when I was due to leave. Having taken 2 years off work, rented out my house and put my stuff into storage I was kind of committed. I rang and they promised to sort it out in situ, which they did.
However, I'd echo the solid advice on visas. I was dealing with reputable universities, if that isn't an oxymoron. Some outfit that gives itself pretentious handles like "international", and throws in an English speaking country like Canada for good measure has to be dodgy.