I need to know the Canadian (Ontario) laws applying to advertising in apartment
buildings, specifically off campus student residences.  I own several
buildings and would like to advestise others services I provide
through various media boards posted throughout the building.  However
I don't know exactly where I am allowed to post them.  Can I put
advertisements right in the rental unit if I have the students
permission? or should I just concentrate on the common areas?  Its
likely that I wouldn't be able to advertise things like cigarettes to
students but exactly what are the limitations?  A direct answer or any
exact sources would be appreciated.  I looked at e-laws.com but
couldn't find anything specific.

IANAL, but... wouldn't this be more of a landlord restriction than a
legal one? Surely the owner of a property has reasonable jurisdiction
over what can be displayed within the owner's property.

I'd guess that you'd have issues with "reasonable expectations of
privacy" if you plan to advertise by actually entering a rented room.

I'd also guess that unless the product was illegal to advertise, and
that would be a societal issue (drugs, pr0n, alcohol to under-age,
etc..) you have reasonable ability to advertise whatever you want in a
place you own. Although, for sanity sake, might I kindly suggest it'd
remain under commons areas? If you have permission from your tenants,
you should be allowed to do what you've been given permission to do,
and no more.

Also consider the people who are renting. After a while, real-life
pop-ups can be annoying as well :).

I am not a Google Answers researcher. disclaimer below applies.