I saw one that would cost $30 per tread x 30 treads.

Look outside the city centers to places that are less treaded by other investors.

Tread lightly. 

Some people are treading dangerously here, giving legal advice that is often illegal.

I think hoarding is now considered an illness as well, so another thing to tread carefully with.   

Tread carefully.  

This is another example where not all jurisdictions have the same laws, so tread carefully when making blanket statements as if they apply everywhere.

At first the plan was to do buy and hold so we've been treading water just saving money.

If her lease in effect, and if she is on any type of government assisted living it would behoove you to tread lightly.

If I were you I would tread carefully and do some research into Ontario Fair Housing statutes before I 'prefer' students over families or vice versa, for my rental unit(s), unless they are under the very same roof I live under too and were part of my 'fraternity' or what ever as housemates etc.http://www.ohrc.on.ca/sites/default/files/attachments/Human_Rights_and_Rental_Housing_in_Ontario%3A_Background_Paper.pdf