Although mental instability may be a factor in this equation, trying to build mutual respect and understanding is a good place to start.

But I'm just trying to figure out how different factors play into each other and how to come up with common metrics, and learning what to look for to determine what a "good deal" means to me.

CAP rate vs ROI : https://www.stessa.com/blog/ca...This site uses 50% rule for operating expenses, I've also seen 30-35% used - use your own judgement when calculating, depends on several factors like age of property, type of tenants, weather/location, etc.

While the interest rate on the loan is important, it shouldn't be the that factor that breaks your investment. 

I’m sure there are many other factors in answering this question. 

Can I eliminate Cap Ex for a while and just factor in repairs & maintenance and vacancy?

Obviously these all all things we will discuss and agree on but we need to make sure we are considering all factors when drawing up  our agreements or structuring our business.Is it even a possibility to start an LLC and obtain a mortgage without them calling it due when its transferred?

However, I have been using the BP BRRRR calculator tool for some offers I have made, and my question for the experienced BRRRR investors is this:If you rehab the property to the point where almost everything is new (roof, kitchen, baths, HVAC, electric, etc), why do you still need to factor in 50% of the rent as going towards expenses if you don't expect any?

So, factor that into how you use your estimates.

This will also factor in to the way it can be financed.Another question to ask is why are they selling these properties?