Any ideas would be great!

Another idea could be to see if the HVAC system can be adjusted or modified to better separate the airflow between the units.

Having an idea of the appreciation is an important part of keeping score.

Will follow up to get more details on your idea!

I wish you the best of luck but your idea if scaling is severely flawed. 

However I did note that houses are mostly really old, e.g. 100 years or older... any idea if this poses challenges in things like lead paint presence, outdated wiring, rusty plumbing, etc., or have many of the homes already been updated?   

Quote from @Joshua Christensen: No offense, but that's a terrible idea!

I like the idea of using a HELOC over a personal loan and going with option 2, but it depends on what your goals are.

What I have learned is that it's nerve wracking to invest out of state, but sometimes investing out of state is a great idea since it could be the most bang for your buck.

Additionally, it's a good idea to connect with a Property Manager early on.