This applicant did not have no credit or insufficient credit. 

I discovered it when I went over there for routine maintenance, and told them that it was:A) Against their lease to modify the property without my written consent.B) Illegal to put a bedroom in the basement (insufficient methods of egress).C) A bad idea, because the basement gets damp with heavy rains.D) Improperly wired.I read them the part in the lease that they had verbally agreed to and signed, told them not to try that again, and they agreed to undo their electric work and remove the furniture from the basement. 

The lender will surely want to loan for less than market value of the collateral, so there would be insufficient loan proceeds to pay off the HELOC. 

You left yourself insufficient time for the turnover. 

You fail to use a buyer's agent and get insufficient disclosures and maybe much worse.

In cities where ADU's have a history there has been no over-saturation of them, which is why there was no heartburn by legislators to amend the bill with a sunset provision to the issue.Thirty years ago in my city developers were allowed to knock down a SFR and replace it with a three-story 8 unit behemoth with vastly insufficient parking.

If so, it's going to be hard to argue now that the door is suddenly insufficient since it's the same door that was on there when you agreed to rent the unit.With that being said, I do understand your concern. 

Wear and tear is an issue and in general I find that student rentals provide insufficient premium in rent to compensate for the additional management time required.I think you can do better if your units are well located and in good condition.

Insufficient, unstable, somewhat non-garnisheable income. 

So the neighbor had provided insufficient notice of the ongoing nature of the issue to me -- plus has failed to take reasonable self-help measures.