She told me that the listing agent has all the tenants contact info and he also ignores her communications, etc for months. 

I suggest you look up the Fannie/Freddie rules regarding ADUs being added to multiplex properties.I will add that I have seen the rule not allowing F/F on multiplex with ADU be ignored, but I also have heard of many cases of it not being ignored.Safest approach is to go with the rule against F/F financing on a multiplex with ADU will be enforced and that F/F financing is not going to be available for this quad with an ADU. 

She told me that the listing agent has all the tenants contact info and he also ignores her communications, etc for months.

Run your calculations with your own expense ratio and ignore theirs until you see proof. 

Don't ignore your property because you think your tenants are good and quiet.

(forgive my ignorance!)

Most leases require tenants to promptly report maintenance issues to protect occupants and the property from ongoing damage.If you ignored these issues for weeks/months, your lease may make you liable for the water bill AND the damages.

Of course higher rates mean higher payments, so at some point it affects the math too much to ignore.

Several calls and texts ignored to the point that I had to contact my loan originator from a different phone number so he would answer.

Hypothetical scenario, ignoring closing costs and commissions and fees to simplify things, just trying to gain better understanding.In this scenario a home is purchased for $100,000 with a $100,000 mortgage.