This behavior needs to be known so it does not continue.

And yes, you're thinking, but your contract says that accepting late rent doesn't waive your right to collect it on the 1st - but what happens is, your behavior ends up waiving the due date by accepting it late.I've heard of landlords who love late fees, as it's extra profit. 

Their phone behavior is a clue as well.

I'd change the no excessive late payments to no more than one late payment - otherwise, it's too subjective.You can add lots of other things like - smelling like smoke, rude behavior, unruly kids, bickering adults, adults yelling at kids, showing up with rude friends, filthy vehicle, having someone other than applicant who is doing all the talking, showing up late, sounding drunk when they leave a voicemail, not filling out application completely, asking for lots of changes like new carpet or paint (they'll be difficult to deal with), tenants who never ask where the laundry is or look to see how big the closets are or ask about parking (they are desperate to take anything), not bringing documents when they said they would -- the longer the legal list you have, the better. 

I left tens of thousands on the table by offering discounted rent in exchange for good behavior except in many cases they were not that great of a tenant after all...I raised rents on two units recently and that's an extra 4.2K a year for me. 3 trips to Vegas all expenses included.

You want to use a nominee as trustee so your name is not displayed.

Having this type of behavior from the tenants is just unacceptable in my opinion. 

I believe your behavior has taught her it is okay to pay late.

A co-signer does not guarantee good behavior, or zero damage, or zero noise, or zero people parking on the lawn or smoking in the house, or bringing in pets or having loud parties, on and on.  

When showing the house, I try to tune in on the prospects, listening to the questions they ask, what they say and watching their behavior.