However after reading rich dad, poor dad, I feel I am letting the aspect of the money control me!

How would you build that into a agreements or is that just the relational aspect and due diligence on the sellers part?

For CAPEX think roof replacement, HVAC replacement, big things that you'll save for overtime. 

More likely you may be at end-of-life for a roof, HVAC systems are about to die, etc.

And if mom won't accept money now, she'll go through the roof if she finds out you want to buy the house for more than it's worth AND give her a monthly break on rent.  

There are Portland zoning rules that allow ADUs in the setback, as long as they conform to certain standards (no windows on the property line side, height restricted at 15 feet through the middle of the gable, medium roof pitch, etc.).  

There were structural and roofing issues that were discovered during inspection. 

My family's farm is multi-generational (currently 6th generation, to be exact), so I have been exposed many of the aspects and tangents of RE via involvement with the family business including generational wealth management, land acquisition, rental homes, tenants, etc. 

I drove by today and the place will need a new stairs and new roof.

It is a good community to network and learn about all aspects of real-estate investing.