The basement is dry as hell, and it's nicely decorated.QUESTION:  What types of financing, financial assistance and tax benefits does one get from being a registered landmark in a historical district? 

It will familiarize you with the basic terminology and benefits.

Your mentor has needs; try to meet them and develop a mutually beneficial relationship.A mentor can benefit your growth, but it's not as simple as one post on a forum full of strangers.

Would there be other tax benefits for high wage earners and what would those be?  

Rarely are there benefits to the seller to structure a transaction in the various ways you propose. 

You can also write it off as a business expense and there could be additional tax benefits for energy efficient home improvements.  

I have not consolidated them under one LLC as of yet—my attorney advised me to beware of franchise taxes in my state that may cancel out the benefits of consolidation.  

Ensure the appraiser accounted for things like the square footage, recent improvements, location benefits, or other factors that impact value.

The other electric meter I pay for because it feeds 2 units (the first floor and basement).1)Would this be a good investment with worthwhile tax benefits?

I can see the benefits to either option: having 5 properties cash flowing as much or more than 10+ levered properties is powerful and takes a lot of stress off of you.