Other than an inspection and appraisal to validate the safety of the unpermitted structure and property value, are there any other suggestions with regard to ensuring the deal is worth pursuing?

I am exhausting all of my options before selling.

For example, has the exhaust hood above the stove been cleaned, including the pipe to the exterior?

So if I would spend more than an hour a month dealing with tenants, then it's a cost savings by hiring this out to a PM - not to mention the headaches and time savings.With that said, you still should know enough about the subject that you can monitor the PM and be sure they are doing a good job.

Just the contribution alone (which is 10X higher than an IRA) is worth it!

Just FYI:I think the tandem house form can also be used in RH-3A.Tandem houses are far better than an ADU because:1.  

There are companies that do exhaustive market research on zip codes, income levels, demographics etc. and sell their research to companies primarily and research institutions secondarily.  

All exterior outlets and outlets within six feet of a water source should be GFCI protected.The bathroom exhaust fan was loud and should be serviced or replaced soon.Alarms and DetectorsThere were no carbon monoxide detectors in the home and one should be installed within 15 feet of every bedroom.InteriorSeveral windows were quite weathered and wornThe glazing was cracking om most windowsSeveral windows had weak or failing sash supportsThe left side rear window did not close properlyThere were previous moisture stains on the right rear bedroom ceiling that were dry at time of inspection, but should be monitored for action.

Account Closed my residential loans hinging on debt to income ratio have been exhausted.

In this day and age, nobody should wait longer than an hour for a return phone call.