Didn't read it all as it was all drama.Think about how much time this tenant is wasting of your life physically and mentally every day, week, month.Once you calculate that paying the rent isn't enough to keep them as a tenant.

Rationale is why bother to talk yourself into accepting them (scarcity mentality) instead of finding another "cleaner" tenant (abundance mentality).  

You can have the "I'll grind it out/sacrifice now, so I can live great when I'm 60" mentality only for so long.

As Sue suggests, I would prorate the rent for next month a bit, and then put a mental note that this tenant will be out the first opportunity you get, whether it's a late rent or lease up. 

The third bedroom (the smallest) was going to be occupied by the mentally challenged teenager, and the two remaining children who "could watch over him". 

(who is not a licensed mental health professional) that her young son has attention deficit disorder and a service animal would mitigate the symptoms he is experiencing. 

Landlords that do not quickly adopt this mentality are targets for the vast number of professional tenants in Ontario.

Don't mentally kill/write off this deal because then it will be gone. 

:  My parents are the traditional "Poor Dad" mentality and I would like to make this mutually beneficial for both them and I.  

On the other hand, you definitely have to consider what other investors are thinking and what their mentality is about buying and how much the 70% rule is ingrained in us.