@Scott Gammenthaler a properly functioning window will not slam down and break a finger.

The zoning enforcement officer shall require that a declaration of the accessory family dwelling unit for the family member, or members, and its restrictions be recorded in the land evidence records and filed with the zoning enforcement officer and the building official.

I had them draft an official letter to the neighbor and the HOA. 

Send the proper notices, charge the appropriate fees, and move on.

The fact they are complaining online might be an indication the property manager dealt with them properly so be sure to ask the manager for their side of the story.7.

This would be my first official unit in my portfolio.I would like to manage it myself if possible as to keep my cash flow higher.

If your books are kept up to date and properly maintained you will be able to calculate whichever ROI you are looking to quantify at any time.

I can't properly waterproof my basement without having theirs waterproofed as well.

I have found "Proper" to be "improper" in almost every quote I have gotten - they were twice or more as anyone else.

If you are just looking to make a deal, being able to do proper due diligence, analyze the deal, remodel a house, etc.