Both units are identical: they are each 3b1b, 1,035 sqft, and single car garage with street parking.Currently I have 3 groups of tenants who I'd like to rent to but cannot decide who are the best 2 out of 3:1. 

Ontario Human Rights Code:People cannot be refused an apartment, harassed by a housing provider or other tenants, or otherwise treated unfairly because of one or more of the following Ontario Human Rights Code grounds: race, colour or ethnic backgroundreligious beliefs or practicesancestry, including individuals of Aboriginal descentplace of origincitizenship, including refugee statussex (including pregnancy and gender identity)family statusmarital status, including those with a same-sex partnerdisabilitysexual orientationage, including individuals who are 16 or 17 years old and no longerliving with their parentsreceipt of public assistance.

Since you guys pretty much don't have a leg to stand on to say no, at least this way you can get a little extra rent and can formally add the minor to the lease (no recourse there but still prudent to have all residents listed) and can ask for some proof of identity and age (possibly some kind of school ID or birth certificate since she won't have a license yet).  

Here is the Seattle definition: “Discrimination” means any conduct, whether by single act or as part of a practice, the effect of which is to adversely affect or differentiate between or among individuals or groups of individuals, because of race, color, creed, religion, ancestry, national origin, age, sex, marital status, parental status, sexual orientation, gender identity, political ideology, honorably discharged veteran or military status, alternative source of income, participation in a Section 8 or other subsidy program, the presence of any disability, or the use of a service animal by a disabled person.

I found an article where State attorney sued his previous company and fined up over six figures for fraudulent dealings - I won't go in details to protect the identity. 

I'm in a near identical situation with a landlord who doesn't care to correct.

I will say that we do still have two properties that are currently on Airbnb, and those two properties in particular we haven't had much of an issue with.Compare that to the nightmare rental we had in Pill Hill (which was the source of probably 2/3 of the horror stories, yet identically furnished), and I think the consensus through this thread is that it's all about location.

This is why most were tiny studios, and why they were not identical - they had to work with the space they had.

A few years ago I approved a couple who were "rejected" by SmartMove because they were recent immigrants, and the app had difficulty verifying their identities.

It would end up being mathematically identical, assuming everyone is doing their math correctly.